The car you mentioned does sound awfully good for a sub $10k car. Make sure you get it on a lift to make sure it hasn't been wrecked and repaired. As these cars get older, more and more of them have lead hard lives.
Check the rear subframe mounts. These rarely fail, but it does happen.
The headliners fall down, the door panels become unglued, and some of the interior pieces break over time. (cheap plastic) The Luxury seats are heavy and mediocre, but the "Vader" seats don't fit everyone well. Make sure you can get comfortable.
Rear strut-mount bushings are a common wear item. (clunking toward back of car), as is the mentioned cooling system.
The engines are pretty bulletproof, but the VANOS system can get a little ticky with age, especially after hard use.
They are wonderful machines. My 97 has 143K miles on it, and I drove it 200 miles yesterday. 27.4 mpg (according to on board computer) and that included a couple of full-throttle runs past 100mph!
It is the best car I've ever owned. Even after 14 years and a bunch of miles, it is solid, stable, fast-enough, and easy to work on.
I am lucky enough to be able to drive a lot of new cars. The E36 M3 is still one of my all-time favorites:
http://grassrootsmotorsports.com/project-cars/1997-bmw-m3/