90BHP (or what's left of it) will be fine to start off with. Will adding the Webber carbs make any difference to the power output?
I will be looking out for the body condition. I would look for rust in the bay and boot, ask the owner if I can look under the carpet at the floorpan, under the bottom of the car if possible, take a magnet to see if filler has been used to patch anything up, check panel gaps and so on.
I'm sure you may have figured it out, but just in case, the subject of age, insurance prices, and having no NCB came up as major issues because this would be my first car.
Luckily being a bit brighter than most teenage yobbos you see driving around I understand what will wreck an engine, how to take care of a car, and most importantly - the basic laws of physics.
I have no interest in driving like a moron, drifting, or being a 'scene kid'. I don't want an E30 to 'look cool' and drift it. I value life and want an E30 because I love the way they look, and would like a car with a bit more character which I can take care of. I am also very interested in being a part of a motoring community. The one I have found here, and E30/BMW/classic car meetups fit the bill nicely.
I grew up watching my dad create these fantastic vintage motorbikes out of piles of rusted parts which he aquired from all over the place. I used to sit there, fascinated, and he used to tell me what he was doing every step of the way and why haha. Ever since then I have had an interest in older bikes and cars.
I know how to sort out rust and such and I have a vast array of tools at my disposal due to the interests Dad has and the fact he is an engineer. I like to think that armed with the internet, the experienced E30 owners on here, BMW parts lists, schematics, the members E30 market, eBay, the tools, and the help of my Dad in areas where I am less confident, that I will be fine. The experience, along with the potential for things to go wrong and require attention, is one I am all up for if it doesn't break the bank.