You need to check with a real estate attorney as laws differ by state. You would think that if they are in a property that you own, they are trespassing. But to avoid any legal issues, you should determine what necessary actions need to be taken to legally get them out of the home. If they are unwilling to leave, you may need to have the county sheriff move them out. You may want to request the lender, prior to closing your deal, to make sure the home is vacated.