Major Dilemma

First of all thank you for spending time to read this and reply if you can. Alright parents own/rent a 3br 1bath home across the street from me worth about $230,000, they live across town in a 4br 3abth home worth $350,000. The dilemma is that both the rental property and the home they live in are behind. I'm in a position to purchase the rental property but only for $120,000 they only have about $24,000 left to pay on it, I don't want to make it seem like i'm trying to steal the house away from them but if something isn't done they're probally gonna loose the rental property. I'm trying to figure out the best course of action so that they put money in their pocket even if they no longer have the rental property. What can I do to help the out as well as help myself. Again thanks for your comments