IMHO, if covered by insurance, $9,000 damage (MB parts and labour)to a Mercedes-Benz could not have been very extensive. My wife rear-ended a Corolla at 5MPH, the visual damage was minor and, yet, the tab was $2,000. Of course, there is risk in buying a damaged car; however, it could turn out to be an excellent investment if the repairs were OK and the price was right. If you are not a risk taker pay more for a car that hasn't been in accidents. Personally, I would buy it if, in addition to normal inspections and precautions, the following conditions were met:
a) the price is significantly lower (i.e. at least $6,000-7,000) than what a similar car with no accidents would sell for;
b) an extended test drive over the weekend doesn't reveal any problems;
c) the tires don't show any abnormal wear patterns (beware if new tires have been installed);
d) a qualified independent shop doesn't report any problems in performing a front end alignment; and,
e) a qualified independent body shop inspects the front end repairs (visual and measurements) and gives the car a clean bill of health.