I would agree too that $4000 is great if he'll let it go for that! One thing you mentioned has me wondering, he had rust repaired! I'd look this car over real well, as I mentioned in the above post areas prone to rust.
It all depends on how you drive it, and how well you keep maintenance. Do you have a lead foot, like to hit the shift points hard, race the engine up near red-line just to hear it roar, careless to pot holes, brake hard, turn hard, ya! it'll become a shop queen, and keep your wallet sterilized!
I have always driven my cars light and easy and have never blown a tranny, or engine, or any major repairs that I can ever recall. I always drive a car to 300K before going on to the next usually, that from over the past 33 years.
If you buy, (my opinion) change all fluids to synthetic, including tranny, engine, rear differential, and break fluid too. Have the wheel bearings re-packed. Because these engines have aluminum heads, flush the engine of green anti-freeze and replace with MB low ph pink anti-freeze.
There are many ways to avoid expensive repairs, I've just listed my way about doing such and I know it works for me and can work for anyone.
Hope you get it..........BB