light damage and high miles are not a issue
sold under 20,000 must be 2000-06.

I highly doubt you're going to find an M3 of that year for that kind of money. If you're looking at a 2001 (there is no 2000) you're looking at about $25,000.
You can find an M3 from earlier years for MUCH less, but it's an entirely different car.

oh you'll find m3's all right for under 20k. it's just who knows how well the prior owner treated them. or if he wrecked it and fixed it himself.

cheaper the car = the worst the condition

you get what you pay for.

Ok, what is your question? Are you asking where to find them?
Check some forum boards and Check these websites and you will probably find some:

If you're looking for that price range, the car will have to be nearly totaled. The 01 m3 is still selling for about $22,000 on Ebay with 90,000 miles. If you wanted, you could buy an e36 M3 and modify it...