How much would you pay or whats it worth
The biggest thing I see is you're taking his word on the condition of the car, and trying to come up with a value based on your interpretation of that. I've looked at stuff people call "solid" and think to myself that "I've scrapped better stuff than this". Also, you have no clue what's hiding under the primer. I would never trust someone else's handy work and assume that you can just throw paint over what they have done. That's a good way to redo a paint job. In my personal opinion, to do it right, the car will need stripped back down and the body work started over. Good luck with it, and if you get it post up some pics.