Some cities have created ordinances that say for a landlord to rent a room out as a bedroom it must have a source of heat and closet and a window that can be opened. more than once i have seen people like a old friend of mine from long ago that used a day bed in the living room of a 1 bed apartment and had a roomate for the other actual bedroom and roomate with the bedroom paid a bit more than half the rent and half the electric and telephone . BUT again if a city has not addressed it via a ordinance and lease didnt limit the number of bodies or how rooms could not be used then the only option the LL has is to wait until the lease would come up for renewal and refuse to renew and give notice to vacate.