Definitely buy one. They're great cars. The e30 is more athletic and the e36 is more refined. Be prepared to do a lot of work on either one though...
Overheating is a critical issue on these cars, the cooling system is finicky & under-engineered. It's a worthwhile sacrifice because it cuts a lot of weight off the front end, which makes the cars really fun to drive. Mine has almost 280k miles, so mileage isn't an issue as much an maintenance. Check for solid paperwork - repair work that's been done, owner's manual with the car, stamps in the maintenance book, etc.
The cam chain seems to be problematic too. It's a noisy engine to start with, but if the engine makes a lot of rasping or clacking noises at idle, walk away. A wandering idle isn't a good sign either, but that's usually fixable. Check the motor mounts for oil leaks too...they're peculiar to the four-cylinders & are very expensive to replace (~$130 each).
I'd also be careful with the usual rust spots on the e30 chassis (maybe shop on rainy days). Door & panel rust is trivial, so you can safely ignore damage to the front apron, spoiler, hood & trunk, front quarters & sunroof panel. The bad places for rust...leaks under the dash (windshield, plenum or firewall leaks), around the upper trunk seal, in the rear seat floor pan (bottoming out pops the seam sealant). Any rust at all in the frame rail...unless you're totally sure it's only on the surface...walk away. I bought a parts car that you could see daylight through the side rail with the doors closed! Likewise for the front frame rails under the driver & passenger footwells...
I'm not as familiar with the e36, but I've seen awful rust in the rear arch, especially in the early 92-93 cars. They also have a reputation for poor electrical reliability and interior durability.
Then there are the mechanical e30 issues...power steering leaks, shot front suspension arms, oil leaks from all over, rear shock mounts, plugged brake lines, bad bearings, etc.
Topic: Looking for a 1991 e30 M42 (Read 4076 times)