I've owned a couple of 320i cars back in the day, they were good cars but slow. An automatic would lose races to city busses that did not even know you were racing, as the old saying goes.
The real world, "flipping" value of the car you describe is under $1k, and that's if it's perfect. Otherwise, you would have to literally give it away. We are living in a world so clogged with used cars that late model (late '90s) cars are sometimes available for a couple thousand dollars w/ 100k+ miles. A 30 y.o. BMW that is not remotely collectible is in the hundreds, not the thousands. Hell, even mildly collectible cars are practically worthless these days as fears of $5.00 gas dampen all enthusiasm for cars in general for most people. (Does not apply to truly collectible stuff).
Look on ebay under "completed auctions" for 3-series BMWs, that is what they are really worth. Your mileage may (not) vary, it's harsh reality.
I would be happy to assist in any way, including driving you around to look at cars if you want. I'm an animal when it comes to scoring deals. Let me know.