Buying house from father

[Craig Herman]

Hello,I live in PA and I am able to purchase a duplex from my father for what is left on the loan. (70k) worth about 250k. He is 76 yrs old and a smoker otherwise in good health. What would be the best way to purchase the property? I know if he falls ill in the next 5 yrs the property could be somehow part of his estate if he were to just sign it over. Just wondering if there are other ways to purchase it to avoid a possible snag in the future. Thanks in advance