Legal Question in Real Estate Law in Georgia

Generally, they are legal. Since you provided no facts about the terms of any contracts, no one can guess whether there might be issues with her particular situation. As for not being able to refinance at the end of the term (again, you did not tell us what "term"), that is always something to consider before entering into the contract, and accepting this risk, in the first place. These deals are often done by buyers who can't afford a home and should not try to buy in the first place, and by sellers/lenders who take advantage of them.