Be vary wary of one for that money mate you'l struggled to find a good one thats not gunna need a lot spending on it, you can spend 2k on one in a heartbeat. Id advise you to save for a bit longer and buy a better car to start with rather than chuck money at one that will only ever be ok.
Lots to look out for- the boot floor cracks on them, can be done under warranty by bmw if under 10yrs old but doubt you'd get one for that budget, its anout a 5k fix at a dealer! Headgaskets going are getting common and difficult to diagnose, rear trailing arm bushes go often, rear springs snap often, tyres are £750-£800 a set for decent ones, servicing is expensive and very important thats its done right, an insp 2 is 600-800 as the valve clearances need to be adjusted which is often missed as its a big job, all parts are expensive and a lot of stuff is bmw only, wheels corrode and expensive to refurb to name a few, there is lots of info on m3cutters.com, certainly worth a good read on there about them, oh smg boxes are sposed to be very troublesome and give lots of bother, also there old tech and not very nice to drive, can be very lurchy and jerky and a total pain round town.

Dont get me wrong there a great car but buy one with your eyes open as you can get stung big time, expect to look at a few theres lots of dogs out there