+1 on the giant bobber !!!Off the top of my head Avalon is one of the higher end pontoons so if it has been taken care of you should be fine.
Not much to go wrong with a toon everything is out in the open and easy to inspect, loo for soft spots on the deck and any obvious damage to the tubes and get the engine looked at by a reputable dealer, that si money well spent, a boat wiht a bad engine is nothing more than a giant bobber.