One way to go is where you have a recorded contract to buy it from her and are making payments to her for principle and interest. In my state we call those contract for deed in other states its called a land contract Either way its a formal and recorded at the county recorders office just like a mortgage, it can spell out details like to who you continue to pay if she were to die before the contract is paid off, it could have a balloon payment in a few years or it could be written to allow payment to take place over 10, 12, 15 (or even 20 ) years and even so there is no balloon at the end. Contract for deed protects the buyer in ways that a so called rent to own wouldn't.