Some people really know what they are looking at and can drive a car round the block, be 95% sure of what the car is and accept the last 5% of unknown.

Apparently the call after 15 min car lot guy was not specifically told that " I will be driving the car for 1 + hour and taking it to my mechanic for a pre purchase inspection, do you agree to this? " otherwise he would not have called in 15 min and made such a fuss.

I get the impression our guy is expecting way too much for the type of car / price point he is after. In that case buying a CPO from a MB dealer is the best bet. Sure, deals can be happened upon but that will take some time and work.