Mother obtained home from previous owner in exchange for debt. She later sold home for $1.00 to her son in 1989. Mother died in 2000. Her son is selling the house. Previous owner has now come forward with a scribbled piece of signed by mother(notary signature but no seal) stating that mother agrees to pay previous owner any profits over $30,000.00. Does the sons legal and documented purchase of the home in 1989 overide the mothers agreement with the previous owner since it is a purchase is less than 30,000.00? Would statute of limitations come into play? Is such a scribbled document good in court? This dispute is in Texas.