Either buy one with <50 000km or buy one with over 200 000km that has been well maintained. Old cars are more fun, more "raw" in driving feel, smaller.
However, some people just have to have new cars. If you buy a car around the 150 000km range, there could be a lot of stuff that is just about to need doing (mostly suspension).
With 10k-20k$, I'd definetly spring for a mint E36 M3, but then again that shouldn't be something you put through the rigours of everyday driving (especially winter) if you'd like to keep it mint...
So a more realistic option for you I'd say is go for a mint e39 for ~10-13k. Generally the older you go the more you will get for your money but it could be extremely tedious finding "the right one."
1998 BMW 328is - summer
1994 BMW 325i - daily
1992 BMW 325i - gone
1988 Mercedes Benz 190E 2.3-8V - sold
Last edited by Dr. Flyview; 01-25-2011 at 01:27 PM.