Many TT that age are a great buy, Many are not. All depends on how it was cared for. When you see it. Look at the ceiling on the inside. In the cabinets, and closets. IF you see any water stains. Walk away. Soft spots in the floor. Walk away.
Make sure all the appliances work as they should. Hook up to water and check for leaks. Put some water in the fresh tank and check the pump, Run the AC, and heat.
Some 5 year old TT look 50, and some look new. If it is fased on the paint. Rub some wax on it to see if it will come back. If it does. Good to go. And yeah. You may have to seal the roof fixtures. No matter how well it was cared for. The stuff on the roof dries out.
Good Luck, and enjoy.