I would suggest you look extra hard at past maintainance if you want to buy a 15 year old car. Try to find a one owner or two owner car that's really been looked after.
You pay more for a well maintained car but that's money well spent.
That thousand bucks or whatever that you save buying a ragged out car EVAPORATES in the first year or less. You will find yourself paying lots of money to get your car back to a level of dependability and performance and good looks which you might have already had by shopping with discrimination in the first place.
In short, my take is: one of the best bargains going is paying top dollar for a very well maintained older high quality car like a Mercedes.