Never hurts to ask, but probably down to the individual landlord. Usually a lease is written up once tenants have been chosen. Individual owners probably just use an online generic template (that’s what the family i rented from when I lived in Somerville did) now Im renting from a property management company who had a more custom lease. Basically boils down to a case by case basis. Just be up front with the landlord one who is living in the space. At the end of the day they just want tenants who don’t cause problems and pay rent on time, beyond that the don’t care what sleeping arrangements are.