I just bought an E36 M3. If you pick up a model that has had the maintenence done you will be ok. Otherwise you can look at a decent chunk of money if something serious goes.
Common issues on E36 that are minor are RSM’s and RTAB’s but replacement costs are cheap like $25. Also waterpump is a big must if you get a 95 with the plastic impellar, cheap to put in a new one with metal impellar. I replaced my radiator, waterpump and tstat already and parts were around 350 total so not too bad.
If you get on bimmerforums most vendors have huge deals or group buys for replacement parts that net you a savings from buying OEM. Dealership cost of parts = outrageous for a BMW but buying OEM from those vendors or a few online sites can save you a few hundred.
All in all, I love the E36 as a daily. I have no fear to drive it through winter, and can’t wait to autox/track it. I get about 26 on the highway and 18-20 city. So gas mileage is pretty good even getting on it every now and then.
If you want to pickup a fun DD at a decent price, get an E36 M3. They hold their resale value pretty well too, you can get a 95 with 120k for 9-10 or under 100k for 11-12k depending on the side of the country (anything over on the West coast seems to be 3k+ inflation haha). Even ones with 140k+ miles seem to still be selling for 10k if it is in great shape.
Feel free to pm any question, or Skunk since he has had his a lot longer than me, I am sure he can answer questions for you too regarding the E36.
I am sure quite a few other BMW guys can chime in here too if they read this.