The seller is probably not going to pay off the bank if there is a mortgage. This can be done legally in some cases with a land contract.The seller is responsible for the mortgage payments. There is something in mortgages called a “due on sale” clause that prevents this in most cases.If the seller owns it free and clear they can do what they please.If the seller in a land contract steals the money from the buyer instead of paying the mortgage, the bank can foreclose and the buyer is hosed.