How much is this van worth?

Its a 1983 Ford econoline, very poor condition, same color.
I want to buy this same one from my great-uncle, he has not driven it in years and only drives another car. I want this van so I can travel through a couple states this winter. Tires are most likely flat-lined, rust, dents, not sure if it starts up. My great-uncle has not had contact with the outside world since the 90s(besides me and my other family).

*What would be a fair price to start as an offer?(Take the family discount into consideration!)
*I was thinking around $350 to start the bidding(I don't know if it even runs or not). I would probably go up to 600 max.

Its going to take a lot of work to get it in good shape, but I'm up for it!
Thank you

Added (1). ***BTW: Its not the same van in the picture, just the same year, make, model***

Might be too much to get it going again. Plus the money you will need to get it at least road worthy. I would offer to take it off his hands for free or start the bid at $200 ending it with $500 max. Van sitting idle for all those years is not good, engine might be locked up, tires will need to be replaced, all new brake hydraulic lines and master cylinder, fuel tank dropped and cleaned etc.

750 it has no market.