Sale of Land Contract with Seller. Can seller renege?

[Neddrick G.]

Hello,

Recently,a friend of mine found some land that was for sale by the owner (10 acres). I personally knew the owner so I put them in contact with each other. She owns the land free and clear. She and my friend drew up a land contract in which he put down 20% and agreed on the monthly payments to her. They both signed off on it and had it notarized etc. He called me a few days ago and advised me that he heard that some people had come by the property and were trying to buy it and were supposedly was sent there by the owner of the land. From conversations with him, it appears that he found that both her and her mother's name is on the deed and that the contract was only signed by her. Is this contract still legally binding? Does it require a signature from both names on the deed? Or would this constitutes a contract with only her half?