Bruce and Laura touch on very important factors. First, if the sale is not professionally negotiated, the deal could last a VERY long time. Second, you need to know if you can afford buying the house, and that a lender is willing to lend you the money to do so. The other factor is the owner needs to show the bank a, "hardship." Just saying he doesn't want to be a landlord anymore may not work depending on the bank. So there are clearly more questions on this one than answers. The bottom line is you should have someone work with you on this. Either a Realtor or an Attorney.