Until they actually vacate the premises, they are still tennants. Even when they vacate (without notice) you must wait 30 days from the time you take possession before you can rent it out. So long as they pay the rent, you can't toss em' out. If they don't pay the rent, you must file for eviction and they can live there for free until the judge orders them out and you cannot cut any utilities or you'll go to jail. Ain't it great to be a landlord?
