I was in the same shoes a couple months ago. I'm a recent college grad too, and I ended up going with a CPO'd 335XI coupe. I had it checked out and everything was ok so I went for it. I have no regrets about the car so far. Im at 49k miles now. You can find a good preowned one, it'll just take some time and patience.
You def wont be disappointed if you get a 335 but it will cost more to maintain than a 328 in the long run so keep that in mind (i think it's worth it for the performance you get out of it though). That new 4 series is on its way but if you like the E92 and have the means for a new one go for it, just know that you will get hit with that depreciation like everyone says.
I've been in the car business for a few years and I would advise you to NOT do a balloon program, that payment in the end is a bitch and not worth it IMO. Your better off going new or CPO. Good luck though