Eeek.... $500 is pretty steep. Worth picking up if the price came down? Maybe. Fwiw my FWC was in about the same shape and I paid $250 for it. It is still in rough shape :elkgrin: but it's solid and clean inside and I feel like I've gotten my moneys worth out of it.
With that in mind I'd say if that AC unit and furnace works and if it has a working fridge I'd maybe go as high as $200ish. Biggest concern I see is the roof and canvas (Can you get new canvas for those things?). Are you up for rebuilding the roof? The rest needs a scrub brush, upholstery and some tlc.
Check for major water damage especially around the roof lift mechanisms. Depending on the amount of water damage it could be a fun project IF you don't mind the work.
Andrew