"You'd be getting a perment house and a deep well and the most innocent girl in the world. You don't need no money" (O'Connor, "The Life You Save May Be Your Own" p.57).
This passage reminded me of New Testament of when Christ walked in the desert for forty days. During that time, Christ was tempted by Satan to use his godly powers in wrong ways. In addition, Satan promised Jesus that if he gave into the Devil's demands, Christ would inherit the whole Earth. In that same way, Mr. Shiftlet (Jesus) is tempted by the old mother (Satan) to give in to her offer to marry Lucynell. Here comes the twist: Shiftlet actually gives in to her demand! A classic example of subversion if there ever was one.