A person who is leasing a residential property such as an apartment or home (tenant) may want to have a roommate stay at the leased premises. This is often a boyfriend or girlfriend but may also be a friend or family member who needs a place to stay for a short period of time—which then becomes a longer period of time.

If the tenant’s relationship with their guest takes a turn for the worse, or if the guest overstays their welcome, the tenant may not be able to remove or evict the guest from the leased premises (apartment or house) as quickly as the tenant imagined. Laws vary from state to state, but in some states such a guest who is not on the lease may become a legal tenant with certain rights after staying at the leased premises for a certain period of time. For example, the guest may become a month-to-month tenant with the right to at least 30 days written notice to move out or vacate the leased premises.

Having a roommate who has not been approved by the landlord and who has not signed and agreed to the terms of the lease agreement (is not on the lease) can cause additional legal problems for the tenant who signed the lease agreement. For example, most residential lease agreements limit the number of days (and nights) a person who has not signed the lease agreement (a guest) can stay at the leased premises. If a tenant violates this provision of the lease agreement by having guests for longer periods of time, the landlord may be able to terminate the lease and evict the tenant.

In New York, tenants have the right to take in a roommate under Real Property Law § 235-f, commonly known as the 'Roommate Law.' This law allows a lease-holding tenant to share their apartment with one additional occupant plus the occupants' dependent children, provided the tenant or the tenant's spouse occupies the premises as their primary residence. If a tenant's guest or roommate stays for an extended period, they may establish tenancy rights, which could require the tenant to go through a formal eviction process to remove them. This process involves providing proper notice, which for a month-to-month tenant typically means giving at least 30 days' written notice. Additionally, lease agreements often have clauses that limit the duration of guest stays, and violating these terms can lead to the landlord taking action to terminate the lease. It is important for tenants to obtain the landlord's approval for any long-term guests or roommates to avoid breaching the lease agreement and facing potential eviction.