Well, this will be a fun year ahead! First off, this is a serious situation, as you know. I think during a foreclosure, details like leases fall through the cracks until the new owner realizes he needs those details. Yes, part of the due diligence and the closing process would ideally have provided estoppel certificates; however it appears this did not happen for you. First things first, notify all tenants in writing of the change in ownership and management, providing the name, contact information, and where to send rent payments and by what date it is due and will be accepted. Also, include the late fee date. If the property bought was in receivership, you should have received all security deposit monies, as well as all other monies minus the prorated amounts. Since the property was in foreclosure, if the current tenant cannot produce a signed lease agreement, the new owner may offer/demand a new one be created and signed at the time of possession. (I am not an attorney, so check that out with yours.) Then you may indeed have to treat this as a "lease up." Usually Residents will approach you especially since rent will be due very soon on the first, and this will give the new Manager a chance to talk to each person. I am sure there will be many things that you will find that occurred without regard to property rules: pets present and unaccounted for, missing tenants and more vacants than known, renewals not in place and inspections not completed ... but with patience, good communication between all parties and a good manager, the problems will be resolved. Very occasionally, tenants will have gone to the city and registered their leases, but this sounds doubtful in this case. It may work out to your advantage! Good luck!