I bought a low mileage 335i because I couldn't afford and M3 at the time (I thought, but was WAY wrong). If money is an issue and you expect your financial situation to improve, I highly recommend you consider leasing an M3. I paid $30k, USD, for my 335i with 27k miles. That's $600/mo, add in the $7-10k I spend on mods, and it cost me a hell of a lot more in the few years I owned it than the $700/mo. lease payment on my M.
Put another way, I'd have way more $$ in my pocket if I'd just leased an M in the first place.