Bought my 87 300Dt off eBay. I think the key is sticking to the ads that have enough information that one can refute that the car is not as advertised once you view it in person. If the car is not as advertised you can walk. This is how I picked up my 300Dt, and it worked well for me. Being centrally located in Texas and having access to low cost air travel sure gives me a bit of an advatange, as I can easily fly out a driving distance of say 1 to 2k miles to drive the car back to Texas. My car was sold by a broker, which I think helped to scare some competitive bids away, but the broker was very specific in the way and the words that he used to describe the car. I made a point to fly out to inspect/purchase the car within the time period allowed for the deposit to be paid, that way I did not have to give up the deposit sight unseen. Turned out the car was in better shape then advertised, and upon picking it up, I found out that it had $6k in maintenance reciepts from a reputable shop over the last two years as well.The broker picked me up from the airport, had previously checked that all the fluids were topped off, tire pressures good, etc. and he even called that evening to make sure I was getting back to Texas Ok. (Other then a tornado or two in Alabama, I was....)

Sorry to be so verbose. I say just look for the ads that have enough information to determine what the seller is actually saying the condition of the car is, and then if it is not as advertised, don't have an issue with walking away, but if the seller tells you nothing about the car, it is kind of hard to say it is not as advertised.