How do you even know who owns the place now? Go to the county recorder’s office and look? I don’t think I’d turn over keys to someone just because they showed up at my door saying they are now the owner. I think I might even change the locks and wait until I could find out who the new official owner is. And taking the old landlord to court…do you mean the one who defaulted and lost the place? That sounds like a waste of time. I know that the bank that forecloses really wants to get the current renter out, without damage being done. At a minimum, I would ask for my deposit plus moving expenses in exchange for possession and the keys.