Reverse Mortgage question - After death

A friend of more than 62 years old co-own a 500.000 USD house and property in AK.He has to settle a divorce by buying out his wife 50% ownership of the house and property.We would like to help him to retain his dearest wish which is the possibility to live in his house and property by lending him 250.000 USD as a lump sum to pay his wife share.He will then be the only owner and obtain a deed on his name only.In return he will have the privillege to continue to live in his house and property until he passes out. In return of this lend, he wants to leave to property to me when he passes out.He proposed this option to me, it is an agreement that we both wants to agree formally on.My questions is what are the right of his heirs and how can we secure his agreement without going into disputes after he passes away?