You signed a 12-month lease with two tenants in March. In August one of them takes a job three states away, and their replacement — someone you have never screened, never met, and whose name appears on nothing — is already sleeping in the second bedroom. You find out in October when a neighbor mentions it. Now you have an unscreened adult in your property, a lease that may or may not cover them, and a security deposit that one of your original tenants wants back right now.
This is the most common unmanaged risk in small-portfolio rentals. Screening and lease signing get all the attention because they happen at a clean, obvious moment. Occupancy changes happen quietly, mid-term, and most landlords have no process for them at all. The fix is not complicated, but it has to be written down before you need it.
Know the Three Different Things People Call “Subletting”
Tenants use one word for three legally distinct situations, and the distinction determines what you should do.
- Sublease — your original tenant stays on the lease, remains fully liable to you, and rents the space (or part of it) to someone else. You have no direct contract with the subtenant. If rent goes unpaid, you chase your original tenant, not the person actually living there.
- Assignment — the original tenant transfers the whole lease to someone new and, if you sign off, walks away from liability. This is what most departing tenants actually want. It is also the one that leaves you most exposed, because you lose a financially responsible party.
- Roommate addition or substitution — one co-tenant leaves or a new adult joins, and everyone signs a fresh lease or an amendment making all current occupants jointly and severally liable. This is the version you should be steering toward in almost every case.
The reason to push toward the third option is joint and several liability. When four roommates sign one lease with that clause, each one owes the full rent — not a quarter of it. If three pay and one vanishes, you pursue the remaining three for the entire balance, and they sort it out among themselves. Under a sublease you lose that leverage over the new occupant entirely. Under an assignment you lose your original tenant’s liability, which was the thing you actually underwrote.
A sublease means you inherited a tenant someone else picked. A lease amendment means you approved one. The paperwork difference is fifteen minutes; the risk difference is an entire tenancy.
Write the Occupancy Clause Before You Need It
Your lease should answer four questions explicitly. If it does not, you will be negotiating from scratch in the middle of a dispute.
- Who may occupy the unit. Name every adult occupant. Add language that only listed occupants and their minor children may reside there.
- What counts as a guest. Set a numeric threshold — a common standard is no more than 14 consecutive nights or 21 total nights in any 6-month period without written approval. Without a number, “my boyfriend is just visiting” is unfalsifiable and you have lost the argument.
- The approval process for changes. Written request, application and screening for the proposed occupant, your written consent required before move-in, and a stated turnaround (10 business days is reasonable and defensible).
- Whether short-term rentals are permitted. Say it plainly: no listing the unit or any portion of it on Airbnb, Vrbo, or similar platforms. Many standard leases predate these services and say nothing, which tenants read as permission.
Note that in some jurisdictions — New York, San Francisco, and a handful of other cities with roommate or occupancy statutes — you cannot flatly prohibit a tenant from adding one additional occupant, and your consent to a reasonable substitution cannot be unreasonably withheld. Check your state and city rules before you rely on an absolute prohibition. A clause that a court throws out is worse than one written to the actual legal standard, because it teaches the tenant your lease is unenforceable.
Screen the Replacement Exactly Like a New Applicant
The single biggest mistake is treating an incoming roommate as an administrative formality because an existing tenant vouched for them. Your existing tenant is not underwriting the risk — you are.
Run the identical process: full application, credit check, income verification, rental history, and criminal background screening where legally permitted. Apply your published income standard to the new household composition, not to the individual. If your threshold is 3x monthly rent in combined gross household income, recalculate with the departing tenant removed. A $2,400 unit needing $7,200 in combined household income may have qualified comfortably with two earners at $4,000 each; swap one for someone earning $2,600 and the household is now under water at $6,600, and you should say so in writing before you approve anything.
Apply the same criteria to every applicant, every time. Inconsistent screening standards are the most common source of fair housing complaints in small portfolios, and roommate substitutions are where consistency slips most — because it feels informal. Document the standard, document the result, and keep both. Tracking which occupants were screened, when, and against what criteria is the kind of record that decides a case eighteen months later. Apps like KeyLoft let you keep per-property occupant and document records on your phone so the approval trail lives somewhere other than your text messages.
If you would not have rented to this person as a stranger walking in off the street, do not rent to them because your current tenant likes them.
Handle the Security Deposit as a Single Fund
Departing roommates want their share of the deposit back on the day they leave. Say no — and put the reason in the lease.
The deposit secures the unit, not individual people. It is returned once, after the final occupant vacates and the unit is inspected. If a roommate leaves mid-term, the correct mechanic is for the incoming roommate to reimburse the outgoing one directly, outside your involvement, while the deposit stays with you untouched. Your paperwork should acknowledge the new occupant’s interest in the existing deposit without you disbursing anything.
Why this matters: if you refund half the deposit in month 7 and the remaining tenants trash the unit in month 12, you are holding half the protection you underwrote. You also created a second deposit accounting event, which in states with strict deposit statutes and 14-to-30-day return deadlines can expose you to statutory penalties — in some states two or three times the deposit amount — for a return you were never actually required to make.
Do a documented condition assessment at the substitution anyway. Photograph every room, date-stamp the file, and have the incoming occupant acknowledge the condition in writing. It costs twenty minutes and it separates damage caused before the swap from damage caused after.
Ready to put this into practice? Download KeyLoft for Free — it’s free and works offline.
Set Occupancy Limits That Survive Scrutiny
Occupancy limits are legitimate and also the fastest way to trip a familial status discrimination claim if you write them carelessly.
The widely referenced federal benchmark is two persons per bedroom, but it is a starting point, not a safe harbor. Enforcement looks at unit square footage, bedroom size, the age of occupants, the configuration of the unit, and any applicable state or local housing code — which frequently sets its own standard by square footage per occupant. A rigid “two per bedroom” rule applied to deny a family with an infant in a large two-bedroom is exactly the fact pattern that generates complaints.
- Base the limit on the unit, not the household — write it as a property characteristic, not as a judgment about who is applying.
- Check your local code first — municipal occupancy standards override your preference and give you a neutral, defensible number to cite.
- Never count children differently than adults — policies that restrict children specifically, or that steer families toward particular units or floors, are per se problems.
- Apply it to every applicant identically — the limit you enforce on one household is the limit you enforce on all of them.
Deal With the Guest Who Became a Tenant
The hardest version of this problem is the occupant who moved in without approval and has been there for months. Two things are working against you: you may have waived the clause by knowing and doing nothing, and depending on your state, a long-term occupant may have acquired tenancy rights you cannot terminate with a text message.
Move in this order. First, document what you know and when you learned it — dates, observations, the source. Second, send a written notice to cure citing the specific lease provision, with a deadline that matches your state’s statutory cure period. Third, offer the constructive path explicitly: the unauthorized occupant applies, gets screened, and if approved signs onto the lease with an adjusted rent if your lease ties rent to occupant count. Most of these resolve here, because the tenant usually is not trying to defraud you — they just did not know they needed permission.
Only escalate to a lease termination if they refuse to apply, or the applicant fails screening on criteria you apply uniformly. And do not accept rent after serving a notice without a written non-waiver acknowledgment — in many jurisdictions accepting rent after a breach waives your right to act on it.
Speed matters more than severity. A clause you enforce in week two is a policy. The same clause enforced in month nine is a selective one, and that is the version that gets challenged.
Build the Paper Trail as a Habit, Not an Emergency Response
Every occupancy change should generate the same five artifacts: the written request, the screening result, your written approval or denial with the reason, the signed lease amendment, and dated condition photos. Five items, filed by property, retrievable in under a minute.
Most landlords managing three to ten doors do not have a system for this because it does not happen often enough to build a habit around. Then it happens at the worst possible time — you are standing in a unit with a phone and no signal, trying to remember whether the guy in the second bedroom was ever approved. Keeping occupant records, lease amendments, and inspection photos in one place that works without a connection is the entire point of tracking on your phone rather than in a filing cabinet at home. This is the same discipline that independent professionals apply elsewhere: freelancers tracking billable hours and client agreements in Stintly, or contractors documenting change orders and job costs in TrestleBook. The pattern is identical — capture the record at the moment it exists, because reconstructing it later is where money and cases get lost.
One more scheduling note. If you rent to students or to households where roommate turnover is predictable, align your lease end dates with the local turnover season rather than fighting mid-term substitutions all year. A lease that ends in July in a college market will produce clean, full-household turnovers instead of a rolling series of one-person swaps that each require screening, amendments, and inspections. Fewer substitution events is a better outcome than handling substitution events efficiently.
The Short Version
Name every adult occupant in the lease. Define guests numerically. Require written approval for any change and screen every incoming adult against the same published criteria you use for strangers. Keep the deposit intact as a single fund until the last occupant leaves. Base occupancy limits on the unit and your local code, never on who is applying. Act on unauthorized occupants in weeks, not months. Document all of it at the moment it happens.
None of this is about being adversarial with good tenants. The landlords who get burned by occupancy changes are almost never the ones who were too strict — they are the ones who had no written process, approved something informally over text, and discovered eight months later that the person living in their property had never been screened and could not be held responsible for anything. A one-page process and a fifteen-minute amendment is the whole defense.