One lease,
several toothbrushes

Point 1The roommate law's actual grant

New York's Real Property Law 235-f — the roommate law — lets a residential tenant share the apartment with immediate family plus one additional occupant (and that occupant's dependent children), regardless of what the lease says: no-roommate clauses are void against it. The tenant must remain in occupancy, and owners may require notification of the occupant's name — but not approval, screening, or extra rent for the statutory roommate.

The limits owners keep: the law grants one unrelated occupant beyond the named tenants — not unlimited sharing; occupants gain no tenancy rights against the owner (the roommate is the tenant's guest in law, the tenant answers for everything); and subletting — the tenant departing while another pays — is a different regime entirely, consent-based per the lease and the sublet chapters.

Point 2Occupancy's hard ceilings

Above the sharing rights sit the safety ceilings: housing maintenance codes set minimum square footage per occupant, bedrooms have legal definitions (the windowless 'bedroom' chapters), and overcrowding is a violation regardless of everyone's consent. The practical arithmetic for owners: the unit's legal occupancy is calculable, the lease should state the maximum, and enforcement targets genuine overcrowding rather than the ordinary shared household.

The building layer adds house rules: co-ops and condos regulate occupancy consistent with law (they cannot void 235-f either), and their real lever is behavior — noise, guests, common-area rules enforced uniformly. The owner leasing into a building answers to both regimes; the lease's occupancy clause should mirror the stricter.

Point 3Running shared households as an owner

The screening boundary: you screen applicants who will be tenants; the statutory roommate arrives by notification, not application. The underwriting response is the lease's strength — the named tenants' joint liability and guarantees carry the household, whoever else lawfully shares it.

Point 4Co-living operators and the corporate middle

The co-living industry — operators master-leasing or managing units into furnished rooms with services — occupies a regulated middle: legitimate models run on compliant occupancy and 30-day-plus stays, while the room-by-room lockout conversions of illegal-hotel memory died by enforcement. Owners approached by operators should underwrite the model's legality (occupancy math, stay lengths, the building's consent) before the yield pitch.

For the individual owner, the honest takeaway: shared households are the city's normal — priced into the deep rental demand the investment chapters celebrate — and the law's architecture works when papered properly. The failure modes are all documentation failures: the unnamed occupants, the absent liability clauses, the occupancy surprises at renewal. The library's recurring answer applies once more — names on paper, rules in writing, and the law as the framework rather than the obstacle.