Early 80s 300TD wagon - can buy cheap- good deal?

[86560SEL]

My uncle called and said he seen a early 80s 300 TD turbo diesel station wagon for sale. He said that the girl there did not know a lot about it, but it was her grandfathers car that passed away a while back. My uncle is going to call her father later. It has been setting a few years, but it is still in good conditions. He said it was dark blue w/ tan interior. He said there is one small rust blister around one of the lower rocker panels at the jack point. Interior is good and it has 208K. He said they are asking $750. for it. I am not even sure at this point if it will run. Maybe a good battery, some good fuel, it may start right up. My uncle said they may even take $500. if you offered it. What would be a good maximum price for one of these cars in this condition? (running/not running). He has no interest in it, but I may have, as I am looking for something fuel efficient and safe to drive to work. Thanks for any advice.