My Dad just bought a 1986 560sel , a very fast house on wheels, everything works like new on it and it has 80K on the odometer. He paid $6300. He held out until he found the one he would be happy with then drove a hard bargain- check out www.autotrader.com
for a huge listing and don't settle for garbage... it seems to be a buyers market right now and the 560 sel is the best bang for the buck IMHO.
He also bought a 1986 500sl convertible. Also very very cherry with very low miles for around $7000. So for $14000 he got $100,000 worth of mercedes. Both are good DIY cars, not too complicated under the hood.
Set a price and hold-out.. the second you give in you will have regrets..