honestly if I were to get an E36 it would be the 318ti, and I'd go full tilt nasty on the suspension, drop an M3 engine in it, and race the hell out of it. either that or do the suspension and slap a big turbo on the 4 banger.
so far as I've seen the biggest problems with the E36 chassis were fixed in the first couple years. the E30s like mine are fun and plentiful but hard to find in decent shape or low miles(mine has 156k on it) and they are getting old so lots of stuff is going to need replacing. so buying a later E36 325 or 330, putting new bushings and shocks/struts in right away would probably be a good way to go. the aftermarket for those cars is second only to hondas and supras so you'll have no shortage of aftermarket to choose from. the DOHC sixes in those cars are pretty bulletproof and dont take much in the way of maintainence(as opposed to my sohc six that needs valve adjustments fairly often) just change the oil, keep the belts in good repair, and watch the hoses.
the E34 5 series is a nice chassis, very solid, the only real issue with those is the thrust arm bushings for the front end, those wear out right at about 100k miles, easy fix just annoying. I had a 1992 525i 5 speed, dropped a chip in it and it was a blast to drive. the E39 5 series is still pretty expensive but are also nice solid cars. but these are all four door cars, which scream mommy mobile but are like a rolling lounge that you can throw through corners(that and cops harly pay attention to 5ers)