How much to offer for 75 27' Land Yacht?

[The Duck]

I just looked at an Airstream Land Yacht 27' that appears to be a 1975-77 model. I looked in the windows and the floorplan is rear bath, center folding double bed, front couch. The unit was parked with a 'for sale' sign asking $5,000. I haven't called the owner yet, and I wondered what an old AS like this would normally go for? It surely will need some repairs and updating. (For example, I've read on this forum in the past about rear floors needing replacement from the weight of the rear bath.) The shell appears in fine condition with no dents or scrapes. Any estimate on value will be appreciated.

The Duck