I hate to echo so many other threads but usually if you can barely afford a used M3 than the answer is not to get an M3. If you get an 09 than what are you doing about warranty in a year or so? Extended warranty is probably 6k and above. No warranty you are looking at some mega expensive repairs possibly.
Gas alone will probably cost you 500 a month EASY. If you are barely affording a used m3 can you pay 500 a month in gas? Then add insurance on top of that.
Your choice but sounds like you cannot afford it right now.