New owner with big problem

It has happened more than once. Several years ago, my daughter and son-in-law visited an RV show and made a deal with General RV on a new trailer. They ran credit right on the spot and were approved at the agreed upon price. They also agreed to take the show vehicle because the wait for a new one would put them out of camping season. After the show ended, the dealer delivered it to the campground where they were going to keep it full time. Done? No, not hardly. They spent hundreds outfitting it and similar hundreds building a beautiful deck. One day they get a call from General and were told the salesman at the show didn't have the authority to sell it so cheap. They wanted an additional $7000. They didn't have the cash nor were they about to approach the bank, which was one that General suggested. Several calls later, General threatened to come and take the rig back. "Try it" was my daughter's response. She notified the gate guard of what was happening and to not let General in. That was the end of it. General never attempted to take it and my daughter just paid it off this year.