An unauthorized occupant in a co-living house hits differently than it does in a whole-unit rental
In a standard single-lease setup, a landlord discovering an undisclosed partner living there has one relationship to manage. In a per-room co-living house, that same situation affects every other paying tenant who signed a lease expecting a defined set of housemates, and that is where the real exposure sits. Say a five-room house has four signed leases at $750 a room. One tenant's partner moves in without notice and is now using the kitchen, the bathrooms, and the common areas at the same frequency as a full paying occupant. The other three tenants did not agree to that person, the house agreement almost certainly does not permit it, and one of them will eventually complain or leave. The vacancy that follows costs more than the conversation you avoided.
The document question is which clause actually protects you here. An occupancy limit written as a per-room person cap is harder to argue around than a general "no subletting" clause, because the tenant's defense is always that their partner is not subletting, just visiting. If the agreement says the named tenant is the sole authorized occupant of that room and defines overnight stays beyond a specific number of consecutive nights as unauthorized occupancy, you have something to enforce. If it only says subletting requires approval, you are in a much grayer conversation. Most house agreements I see in co-living setups use the subletting language because it was lifted from a standard whole-unit lease, and it does not fit the room-by-room model.
The practical path once you have confirmed the person is living there is a written notice to the tenant on the lease, not to the partner, citing the specific clause and giving a cure period. The cure is either the partner vacates or the partner applies, gets screened, and signs their own room lease if a room is available. That second option is only on the table if you actually have capacity. If the house is full, the partner has to go and the notice should say so plainly. What the notice cannot do is name the partner as a party or treat them as a tenant, because in most jurisdictions that creates a tenancy relationship you did not intend and cannot easily undo.
The harder version of this is when the unauthorized occupant has been there long enough that a judge might view them as a tenant by conduct. That timeline varies by state, which is why this needs a local landlord-tenant attorney to confirm, not a forum post. The mechanism matters though: it is usually not a fixed number of days but a combination of acceptance of rent from or on behalf of that person, knowledge of their presence without objection, and the length of occupancy. If you knew for two months and said nothing, the cure notice lands differently.
What does your current house agreement say on overnight stays, and is the occupancy limit written per room or per property?
