Residential Landlord-Tenant Law: Leases, Habitability, Deposits, and Eviction

Summary. Housing is the area of law where the most people have the most at stake and the least information. This article explains what a lease actually promises, where the implied warranty of habitability came from and what it requires, the four remedies for a landlord who will not repair, how deposits are regulated, why self-help lockouts are illegal nearly everywhere, how summary eviction works, what defenses win, and what happens after judgment.

Something like a third of American households rent, and almost none of them have read their lease closely enough to know what it does. That is not a criticism. Leases are written by landlords' lawyers, presented on a take-it-or-leave-it basis, signed in a hurry by someone who needs somewhere to live by the first of the month, and then filed in a drawer until something goes wrong.

When something does go wrong — the heat fails in January, the deposit does not come back, a notice appears taped to the door — the tenant discovers that housing law is not one body of rules but three stacked on top of each other. There is contract law, because a lease is a contract. There is property law, because a lease is also a conveyance of an interest in land, and some very old doctrine still runs through it. And there is a thick layer of statute — state landlord-tenant acts, local rent and eviction ordinances, federal fair housing and consumer law — enacted specifically because the first two layers produced results legislatures found intolerable.

This article works through all three. It is written for tenants who need to know what they can demand, for landlords who need to know what they can do, and for the lawyers and judges who handle these cases in the highest volume of any civil docket in the country.

Part I: What a lease actually is

A residential lease does two things at once, and the distinction matters more than it sounds.

It conveys a possessory interest. For the term of the lease the tenant, not the landlord, has the right to possess the premises. The landlord retains a reversion — the right to get the property back when the term ends — and whatever rights the lease reserves. This is why a landlord cannot simply walk in whenever they like, and why a landlord who locks a tenant out is not enforcing a contract but committing a trespass on someone else's possessory interest.

It creates mutual contractual promises. The tenant promises to pay rent and comply with the lease. The landlord promises to deliver possession and, in modern law, to maintain the premises.

The old rule, and why it changed. At common law those promises were independent. A tenant's duty to pay rent did not depend on the landlord doing anything at all, because the tenant had received what the lease conveyed — the land. If the roof fell in, that was the tenant's problem; the doctrine had been built for agricultural tenancies where the land was the point and the buildings were incidental.

That rule became indefensible when applied to a fifth-floor apartment with no working furnace, and in 1970 the D.C. Circuit said so in Javins v. First National Realty Corp., 428 F.2d 1071 (D.C. Cir. 1970). Judge Skelly Wright's opinion holds that the old rule rested on factual assumptions that no longer describe urban housing: the modern tenant seeks "a well known package of goods and services," lacks the skill and the legal right to make repairs, and bargains from a position of unequal power in a shortage market. The court held that a warranty of habitability, measured by the housing code, is implied by operation of law into every residential lease, and — crucially — that the tenant's obligation to pay rent is dependent on the landlord's performance of it.

Nearly every state has since adopted the warranty by decision or statute. In most, it cannot be waived, and a lease clause purporting to waive it is void. That single doctrinal move is the foundation of everything in Parts II through IV.

Part II: The implied warranty of habitability

What it requires. The standard formulation is that the premises must be fit for human habitation and comply with applicable housing and building codes in ways that materially affect health and safety. In practice the recurring items are:

Heat in winter, and in a growing number of jurisdictions, cooling in extreme heat
Hot and cold running water
Working plumbing, and sewage that goes where sewage should go
Electrical systems that are safe and functional
A weathertight roof, walls, windows, and doors
Working locks on exterior doors
Freedom from vermin and insect infestation
Structural soundness of floors, stairs, and railings
Smoke and carbon monoxide detectors
Remediation of lead paint hazards in older housing, and increasingly of mold

What it does not require. Cosmetic perfection, new appliances, aesthetic upgrades, or repairs to conditions the tenant caused. A cracked countertop is not a habitability defect. A refrigerator that stops working may or may not be, depending on whether the lease included it and whether local code treats it as essential.

The materiality threshold. Not every code violation breaches the warranty. Courts ask whether the defect materially affects health and safety, considering its nature, duration, the effect on the tenant's use, whether the tenant caused it, and whether the landlord had notice and a reasonable chance to fix it.

Notice is the tenant's first job. Almost every remedy in Part III requires that the landlord had notice of the condition and a reasonable opportunity to repair. Notice should be in writing, dated, specific about the condition, and delivered in a way that can be proved — email, text, certified mail, or a hand-delivered letter with a photographed copy. The single most common reason a habitability defense fails is not that the condition did not exist. It is that the tenant told the superintendent in the hallway and cannot prove it.

Part III: Four remedies for a landlord who will not repair

State law varies substantially on which of these is available and on the conditions attached. Check the local statute before using any of them, because a tenant who withholds rent in a state that does not permit withholding has simply defaulted.

1. Repair and deduct. The tenant arranges the repair, pays for it, and deducts the cost from rent. Statutes typically cap the amount — often one month's rent or a fixed dollar figure — limit how often it may be used in a year, and require prior written notice and a waiting period.

2. Rent withholding. The tenant stops paying and asserts the breach as a defense when the landlord sues. Many states require the withheld rent to be paid into court (escrowed) rather than kept, and a tenant who spends it will usually lose even a strong habitability case. This is the highest-risk remedy and the one most often used incorrectly.

3. Rent abatement. Rather than withholding, the tenant pays and later sues — or defends — for a reduction in rent reflecting the diminished value of the premises. Courts use several measures: the difference between the rent agreed and the fair rental value in the defective condition; a percentage reduction reflecting the portion of the unit or the period affected; or the cost of the tenant's own repairs and expenses.

4. Terminate and leave — constructive eviction. Where the defect is severe enough to render the premises substantially unusable, the tenant may treat the lease as terminated. Three elements: the condition must be caused by the landlord's act or failure to act; it must substantially interfere with the tenant's beneficial use; and — the one that trips people up — the tenant must actually vacate within a reasonable time. A tenant who stays for eight months and then claims constructive eviction has proved that the premises were usable.

Also available: reporting to the local code enforcement or housing inspector, which creates an official record that is powerful evidence and, in most states, triggers anti-retaliation protection; and affirmative suit for damages, which in many states carries statutory penalties and attorney's fees. On fee shifting, see Attorneys Fees and Costs.

A worked example. In November, the furnace in a two-bedroom apartment fails. The tenant emails the landlord that night with a photograph of the thermostat reading 51°F, and follows up in writing on days 3, 7, and 12. Nothing happens. Rent is $1,400. The tenant buys two space heaters ($180), and the electric bill rises $95 over the month.

In a repair-and-deduct state, the tenant hires an HVAC contractor for $640 and deducts it, attaching the invoice to a letter with the next month's rent. In an abatement state, the tenant pays rent and later claims a 40% abatement for the 26 days without heat — roughly $485 — plus the $275 in heaters and electricity. In a withholding state with an escrow requirement, the tenant deposits the $1,400 with the clerk and appears at the hearing with the emails, the photographs, and the code inspector's report. In each version, the emails are what makes it work.

Part IV: Rent, fees, and what a landlord may charge

Rent is due when the lease says it is due, and in most jurisdictions there is no statutory grace period — a lease that says rent is due on the first means the first, and "everyone pays by the fifth" is a practice, not a right.

Late fees are increasingly regulated. Many states cap them by percentage or dollar amount, require that they be stated in the lease, and prohibit compounding. Even absent a statute, a late fee that functions as a penalty rather than a reasonable estimate of the landlord's loss is vulnerable under ordinary contract principles governing liquidated damages.

Junk fees are under scrutiny. Application fees, "administrative" fees, mandatory renters-insurance markups, package-handling fees, and charges for online rent payment have all drawn regulatory attention and legislation in several states, some requiring all-in price disclosure in advertising.

Rent increases. In a fixed-term lease, rent cannot be raised mid-term unless the lease says so. In a month-to-month tenancy, rent may be raised with proper notice — commonly 30 days, but 60 or 90 in many states and for larger increases. Rent-regulated jurisdictions impose their own limits, and a handful of states have adopted statewide caps on annual increases with exemptions for newer construction and small owners.

Application screening. Credit reports and criminal background checks used in tenant screening are consumer reports subject to the Fair Credit Reporting Act, which means a denial based on one triggers an adverse action notice and the applicant's right to dispute inaccuracies. Blanket criminal-record exclusions also raise fair housing exposure under a disparate impact theory (Part VII).

Part V: Security deposits

Deposit disputes are the most common landlord-tenant claim in small claims court, and they are also the most winnable, because the statutes are specific and landlords frequently ignore them.

Typical statutory requirements:

A cap on the amount — commonly one or two months' rent, sometimes more for furnished units or pets.
Segregation — many states require the deposit be held in a separate account, sometimes an interest-bearing one, with the interest belonging to the tenant.
Written notice of where the deposit is held.
A move-in condition report, in a growing number of states, signed by both parties. This is the single most valuable document in any later dispute.
A deadline to return the deposit after the tenancy ends — commonly 14 to 45 days.
An itemized written statement of deductions, with receipts or estimates.
Penalties for noncompliance — frequently double or treble the deposit plus attorney's fees, and in some states forfeiture of the right to withhold anything at all.

What may be deducted: unpaid rent, damage beyond ordinary wear and tear, cleaning to return the unit to its move-in condition (not to a better one), and any charges the statute permits.

What may not: ordinary wear and tear. Carpet worn thin along a hallway after four years is wear. A burn hole is damage. Faded paint is wear. A wall painted magenta without permission is damage. Many states apply depreciation schedules, so a landlord who replaces an eight-year-old carpet with an expected life of ten years may charge only the remaining value.

The tenant's playbook: photograph or video every room at move-in and at move-out, with a timestamp; keep the move-in report; give written notice of the forwarding address, since some statutes make the deadline run from that; and if the deadline passes with nothing, send a demand letter citing the statute and the penalty before filing in small claims. See Small Claims Court.

The landlord's playbook: use a signed move-in report, document with dated photographs, keep receipts, calendar the statutory deadline the day the keys come back, and itemize honestly. The penalty provisions are severe precisely because they are aimed at landlords who treat deposits as additional rent.

Part VI: Entry, privacy, and quiet enjoyment

Every lease carries a covenant of quiet enjoyment — the landlord will not substantially interfere with the tenant's use and possession. It is breached by more than noise: repeated unannounced entries, shutting off utilities, harassment intended to force a move-out, and failure to control a nuisance the landlord has the power to abate.

Entry rules are statutory in most states: notice of a stated period (commonly 24 or 48 hours), entry at reasonable times, and only for enumerated purposes — repairs, inspection, showing the unit, or emergency. A landlord who enters routinely without notice is not merely rude; they are creating a damages claim and, in some states, a statutory penalty.

Utility shutoffs and lockouts are addressed in Part XI, and they are the single most dangerous thing a landlord can do.

Part VII: Discrimination and retaliation

The Fair Housing Act, 42 U.S.C. § 3601 et seq., makes it unlawful to refuse to rent, to discriminate in terms or conditions, or to make discriminatory statements or advertisements because of race, color, religion, sex, familial status, national origin, or disability. The core prohibition is at 42 U.S.C. § 3604, with implementing regulations at 24 C.F.R. Part 100. State and local laws frequently add source of income, sexual orientation, gender identity, age, marital status, and military status.

Disparate impact is available. In Texas Department of Housing & Community Affairs v. Inclusive Communities Project, Inc., 576 U.S. 519 (2015), the Supreme Court held that disparate impact claims are cognizable under the Act, while imposing safeguards — a robust causality requirement, and a burden-shifting framework that lets a defendant justify a policy by a valid interest.

Standing is broad. Trafficante v. Metropolitan Life Insurance Co., 409 U.S. 205 (1972) allowed existing tenants to sue over the loss of the benefits of living in an integrated community, and Havens Realty Corp. v. Coleman, 455 U.S. 363 (1982) held that a tester — someone who inquires about housing with no intention of renting, in order to detect discriminatory practices — has standing when given false information. Testing remains the primary method of proof, because discrimination in housing is rarely announced.

Disability accommodations. Landlords must permit reasonable accommodations in rules and policies (a service or assistance animal despite a no-pets policy; a reserved parking space; a payment date matched to a benefits deposit) and reasonable modifications to the premises at the tenant's expense, with limited exceptions.

Enforcement. A HUD administrative complaint, a state or local agency complaint, or a private civil action under 42 U.S.C. § 3613 — which permits actual and punitive damages and attorney's fees, and has its own limitations period.

Retaliation. Nearly every state prohibits retaliating against a tenant for complaining to the landlord or a housing agency, joining a tenant organization, or asserting statutory rights. Most create a presumption of retaliation for adverse action taken within a set window — often 90 days to a year — after protected activity, which shifts the burden to the landlord to show a legitimate reason. Retaliation is a defense to eviction and, in many states, an affirmative claim.

Part VIII: Ending a tenancy

A fixed-term lease ends on its stated date. Neither party ordinarily needs to give notice, though many leases require notice of intent not to renew, and several states now require it by statute.

A periodic tenancy — month to month, most commonly — continues until either party terminates with proper notice. The default is typically 30 days, but longer periods are now common for landlords, and several states require 60 or 90 days for tenancies over a year.

A holdover tenant who stays past the term may be treated, at the landlord's election, as a trespasser subject to eviction or as a new periodic tenant. Accepting rent after the term generally creates the tenancy, which is why landlords who intend to evict must be careful about what they accept and how they characterize it.

Notice for cause is the beginning of an eviction and comes in three ordinary flavors:

Pay or quit — a demand for unpaid rent, with a short statutory window (often 3 to 14 days) to cure by paying.
Cure or quit — a demand to fix a lease violation within a stated period.
Unconditional quit — no opportunity to cure, available only for enumerated serious grounds in most jurisdictions (repeated violations, illegal activity, serious damage).

Notice defects are the most common reason evictions fail. Wrong amount demanded, wrong number of days, wrong service method, wrong party named, no landlord signature, a demand that includes late fees or utilities in a jurisdiction where only rent may be demanded — each of these can require the landlord to start over. Because the summary process is fast, courts hold the party invoking it to the statute's terms.

Part IX: Eviction — how the summary process works

Eviction is not an ordinary lawsuit. Every state has a summary proceeding — variously called unlawful detainer, forcible entry and detainer, summary process, or simply eviction — designed to decide the single question of who is entitled to possession, quickly.

The Supreme Court has blessed the speed, within limits. In Lindsey v. Normet, 405 U.S. 56 (1972), the Court rejected a due process and equal protection challenge to Oregon's summary process, holding that there is no constitutional right to housing of a particular quality and that a legislature may create an expedited procedure limited to possession — while striking down a requirement that a tenant post a bond of double the rent to appeal.

But the constitutional floor is real. Greene v. Lindsey, 456 U.S. 444 (1982) held that service by posting on an apartment door — where notices were known to be removed by children before tenants saw them — did not satisfy due process where mail service was readily available. And Pernell v. Southall Realty, 416 U.S. 363 (1974) held that the Seventh Amendment guarantees a jury trial in an action to recover possession of real property where the statute permits money damages, at least in the federal enclave the case arose from — and many states guarantee jury trials in eviction by their own constitutions or statutes.

The typical sequence:

Notice served and the cure period expires.
Complaint filed — often on a form, with a filing fee, naming all occupants.
Summons served, with a very short answer deadline: as little as five days in some states, sometimes as few as three.
Answer, raising defenses and any counterclaims the jurisdiction allows.
Hearing, frequently within one to three weeks of filing, on a crowded docket where the average case takes minutes.
Judgment for possession, and in most states for unpaid rent and costs.
Writ of possession issued after a statutory waiting period.
Execution by the sheriff or marshal.

The practical reality is that most tenants do not appear. Default rates in eviction dockets are high, driven by short notice, work conflicts, and confusion about whether appearing matters. It matters enormously: represented and appearing tenants obtain dramatically better outcomes, and a growing number of cities have adopted right-to-counsel programs in eviction for exactly that reason.

Part X: Defenses that actually win

Defective notice — wrong period, wrong amount, wrong service, wrong parties. The most common winner.
Rent was paid, or tendered and refused. Acceptance of rent after a notice generally waives the notice in most jurisdictions.
Breach of the warranty of habitability, raised as a defense to nonpayment, with the rent abated to the value of what was actually provided.
Retaliation, especially within the statutory presumption window.
Discrimination under fair housing law.
Failure to comply with a required pre-suit step — registration of the rental unit, a certificate of occupancy, a required license, or participation in a mandatory mediation or diversion program. In several cities an unregistered landlord cannot maintain an eviction at all.
Waiver — a landlord who has accepted late rent for eighteen months has, in many jurisdictions, waived strict enforcement absent a notice reinstating it.
The eviction is for a protected reason — a tenant organizing, a request for a reasonable accommodation, a code complaint.
Procedural defects — improper service of the summons, a defective complaint, the wrong plaintiff (a management company suing in its own name without authority).
Payment plans and rental assistance, which in many courts convert a possession case into an agreed order rather than a judgment.

Counterclaims — for the deposit, for damages from uninhabitable conditions, for illegal fees — are permitted in some states and barred in others, on the theory that the summary process should decide only possession. Where barred, the tenant may still raise the same facts defensively and file a separate action.

Part XI: After judgment, and the self-help prohibition

The landlord may not do it themselves. Changing the locks, removing the door, shutting off water, heat, or electricity, removing the tenant's belongings, or threatening any of these is illegal in nearly every state, regardless of how much rent is owed and regardless of whether the landlord is right about everything else. Statutes typically provide actual damages, statutory damages of one to three months' rent or a fixed multiple, attorney's fees, and injunctive relief. Some make it a criminal offense.

This is worth stating plainly because it is the mistake that turns a straightforward possession case into a five-figure liability: a landlord who is entirely in the right can be made to pay damages for a lockout.

The lawful path is a writ of possession executed by a law enforcement officer, after the statutory waiting period, with notice to the tenant of the scheduled removal.

Abandoned property is governed by statute in most states: the landlord must store the tenant's belongings for a stated period, give notice, and may dispose of or sell them only after that period, sometimes with an obligation to account for proceeds. Throwing a tenant's possessions on the curb creates its own claim.

The judgment's afterlife. An eviction judgment is a public record, is picked up by tenant screening companies, and can make housing difficult to obtain for years. Several states now permit sealing or expungement of eviction records — automatically where the tenant prevailed or the case was dismissed, and on motion in other circumstances. Where available, it is worth asking for as part of any settlement. On record relief generally, see Expungement and Record Sealing.

Part XII: Situations with their own rules

Subsidized housing. Public housing, Section 8 vouchers, project-based Section 8, and LIHTC properties each carry federal procedural protections that exceed state law — good-cause eviction requirements, grievance procedures, and specific notice content. A tenant with a voucher facing eviction should immediately notify the housing authority, because the voucher itself may be at stake.

Foreclosure of the rental property. The Protecting Tenants at Foreclosure Act gives bona fide tenants the right to remain through the end of the lease term after a foreclosure, with a floor of 90 days' notice, and gives month-to-month tenants at least 90 days. A purchaser who intends to occupy the property as a primary residence may terminate a lease on 90 days' notice. Many states provide more. See Foreclosure and Mortgage Servicing.

Manufactured and mobile home parks. Where the tenant owns the home and rents the lot, most states have separate statutes with longer notice periods, restrictions on the grounds for eviction, and rules about the sale of the home in place — because the cost of moving a manufactured home makes an eviction functionally a forced sale.

Roommates and subtenants. A co-tenant on the lease is jointly and severally liable for the whole rent, not a share. A subtenant has rights against the tenant who sublet, not usually against the landlord. An unauthorized occupant may be a lease violation. And a roommate who is not on the lease and is asked to leave may still be entitled to eviction process rather than a lockout in many states, depending on whether they are a tenant, a licensee, or a lodger.

Short-term rentals and hotels. Occupancy that is transient may fall outside landlord-tenant law entirely — but the line is drawn by statute and by conduct, and a "hotel" guest of eleven months is very likely a tenant.

Domestic violence protections. Most states now allow a survivor to terminate a lease early with documentation, prohibit eviction based on being a victim of domestic violence, and require lock changes on request. Federal protections apply in covered housing programs. See Domestic Violence and Protective Orders.

Part XIII: The view from the landlord's side

Tenant-protective law is not a reason to run a rental business badly, and most of what protects a landlord is done before a problem arises.

Screen lawfully and consistently. Use written criteria, apply them uniformly, comply with the FCRA's adverse action requirements, and avoid blanket criminal exclusions.

Use a lease that complies with your state's statute. Clauses waiving habitability, waiving jury trial, imposing confession of judgment, requiring the tenant to pay the landlord's fees regardless of outcome, or authorizing self-help are void in many states — and in several, including such a clause is itself a violation with penalties attached.

Document everything. A signed move-in report with photographs, dated repair records, and written communications resolve most disputes before they become cases.

Respond to repair requests promptly and in writing. The habitability defense is defeated by a record showing a landlord who answered within a day and had a contractor out within a week.

Serve notices exactly as the statute requires, and have a form reviewed by counsel once rather than fixing it in court repeatedly.

Never use self-help. See Part XI.

Consider whether eviction is the best outcome. A negotiated move-out with a modest sum for keys and a released claim is frequently faster and cheaper than a contested case, and it avoids the risk of a counterclaim.

Part XIV: Rent regulation and just-cause eviction

Two overlays change the analysis in a growing number of places, and a practitioner who does not check for them will give confidently wrong advice.

Rent regulation comes in two generations. The older form — strict rent control, with a fixed maximum rent tied to a base year — survives in a small number of cities and typically applies only to older buildings. The newer and rapidly spreading form is rent stabilization or anti-gouging legislation: an annual cap on increases, usually expressed as a percentage plus inflation, with exemptions for buildings constructed within the last fifteen years or so, for owner-occupied small properties, and sometimes for single-family homes. Several states have now adopted statewide versions. The practical questions are always the same three: Is this unit covered? What is the maximum lawful increase this year? And what notice does an increase require? An increase above the cap is void as to the excess, and in many ordinances the tenant may recover the overcharge with a penalty.

Just-cause eviction ordinances are the more consequential development. Under the traditional rule, a month-to-month tenancy may be ended for any reason or none, with proper notice. A just-cause law reverses that: the landlord must state and prove one of an enumerated list of reasons. Those lists divide into two categories.

At-fault causes — nonpayment, material lease breach, nuisance, criminal activity, refusing a lawful lease renewal, denying access — look like ordinary eviction grounds.

No-fault causes — owner or family move-in, withdrawal of the unit from the rental market, substantial renovation, or demolition — are permitted but carry conditions. Typically the landlord must pay relocation assistance (often one to three months' rent), give extended notice, and observe restrictions on re-renting the unit afterward. A landlord who evicts for owner move-in and then relists the unit at a higher rent two months later faces statutory damages in most such ordinances, and these provisions are actively enforced.

Why this matters for everyone in the case. A just-cause jurisdiction converts eviction from a possession question into a proof question. The landlord must plead the cause, and the notice must state it with the specificity the ordinance requires. A boilerplate 30-day notice that would be perfectly good two towns over is fatally defective here. Tenants and their advocates should therefore make the covered-unit determination the very first research step, before analyzing anything else, because it frequently ends the case.

And the sleeper issue: registration. Many rent-regulated and just-cause jurisdictions require landlords to register units annually and pay a fee. A significant number make registration a precondition to filing an eviction at all. An unregistered landlord in such a city cannot maintain the action regardless of how much rent is owed — a defense that is dispositive, easy to verify online, and routinely overlooked.

Part XV: Frequently asked questions

Can my landlord raise the rent in the middle of my lease? Not unless the lease says so. A fixed-term lease fixes the rent for the term.

My landlord won't make repairs. Can I just stop paying rent? Only in states that permit withholding, usually with an escrow requirement. Get the rule right first — a tenant who withholds where withholding is not allowed is simply in default.

How long does an eviction take? From notice to writ, commonly three to eight weeks, though contested cases and crowded dockets extend it and a few jurisdictions take months.

Can I be evicted without going to court? No. Self-help lockouts and utility shutoffs are illegal nearly everywhere and carry statutory penalties.

Does my landlord have to return my deposit if I broke the lease? The deposit rules still apply. The landlord may deduct lawful damages, including unpaid rent, but must still itemize and meet the deadline — and in most states must mitigate by attempting to re-rent.

Can a landlord refuse to rent to families with children? No. Familial status is protected under the Fair Housing Act, subject to a narrow exemption for qualifying housing for older persons.

What if my roommate stops paying? If you are both on the lease, you are each liable for the full rent. The landlord may pursue either of you, and your remedy against your roommate is a separate claim.

Is my eviction record permanent? Often not. Ask about sealing or expungement in your state, and negotiate for it in any settlement.

Part XVI: For non-lawyers — what to do this week

If you are a tenant:

Find and read your lease. Note the term, the rent, the late fee, the notice provisions, and anything about repairs and deposits.
Put everything in writing from now on. Email or text, so it is dated and preserved. Photograph conditions with the date visible.
If something is broken, give written notice today describing the condition specifically and asking for repair. Follow up in writing.
If you receive a notice or a court paper, do not ignore it. The deadlines are days, not weeks, and the default rate is why landlords win most cases.
Look for free help. Legal aid, tenant unions, court self-help centers, and — in a growing list of cities — right-to-counsel programs.
Never move out because someone told you to over the phone. Only a court order executed by an officer can remove you.

If you are a landlord:

Have your lease and your notice forms reviewed once against your state's statute. It is the cheapest legal work you will ever buy.
Use a signed move-in condition report with photographs.
Calendar the deposit deadline the day you get the keys back.
Answer repair requests in writing, fast.
Serve notices exactly as the statute requires.
Never change the locks.

Primary authority

Javins v. First National Realty Corp., 428 F.2d 1071 (D.C. Cir. 1970) — the implied warranty of habitability and the dependence of the rent covenant.
Lindsey v. Normet, 405 U.S. 56 (1972) — summary eviction procedures upheld; the double-bond appeal requirement struck.
Pernell v. Southall Realty, 416 U.S. 363 (1974) — the Seventh Amendment jury trial right in actions to recover possession.
Greene v. Lindsey, 456 U.S. 444 (1982) — notice by posting held constitutionally inadequate.
Jones v. Alfred H. Mayer Co., 392 U.S. 409 (1968) — 42 U.S.C. § 1982 reaches private racial discrimination in property transactions.
Trafficante v. Metropolitan Life Insurance Co., 409 U.S. 205 (1972) and Havens Realty Corp. v. Coleman, 455 U.S. 363 (1982) — standing under the Fair Housing Act, including tester standing.
Texas Dep't of Housing & Community Affairs v. Inclusive Communities Project, Inc., 576 U.S. 519 (2015) — disparate impact under the FHA.
42 U.S.C. § 3601 · § 3604 · § 3613 — the Fair Housing Act.
24 C.F.R. Part 100 — HUD's implementing regulations.
15 U.S.C. § 1681c — FCRA limits on information in consumer reports used for tenant screening.
Uniform Residential Landlord and Tenant Act (1972, revised 2015), as adopted; the Protecting Tenants at Foreclosure Act, 12 U.S.C. § 5220 note; state landlord-tenant acts and local rent and eviction ordinances.