Oh they aren't all that bad. If you learn how to do things yourself and Bimmerforums.com has some great DIY articles, along with Pelican Parts, you will be fine and you will actually enjoy doing the work yourself as well. My M3 I bought for $6K. After I replaced the suspension (Bilsteins with H&R Sports), bushings (everywhere), VANOS kit from Dr. Vanos, Stewart Water Pump, Borla muffler, belt, fluids, X-brace, Turner Reinforcement Kit front and rear, Fluidyne V3 Aluminum Radiator, clutch fan, B&R Short Throw Kit, etc. my bill came out to $5800. But now, since a lot of the major maintenance is done, I am looking at a good 90K before I have to do it all again, except I will be spending a lot less.
I only did this because I was an idiot. But the M3 is one of my boyhood dream cars. I saved too long for it and now will be waiting to give it some fresh paint, new door cards, and eventually installing my black Vader seats (front and rear).