Well, I’m not sure what condition the cars you’re looking at are in, but some examples of problems I’ve dealt with include ABS modules, turbos, electrical gremlins (windows going up and down for no reason, sunroof malfunctioning), locks not working, radio not being able to tune in anything, various engine sensors, shitty exhaust…
On the other hand between my brother and I we have owned 4 e36 BMW’s of various years/models and they have been far better. Better to drive, better to maintain, etc.