I agree with Jeff, but would add that driver/owner skill and driving habits are also major factor in the longevity and cost of ownership. I am not a DIYer, but my car gets its regular maintenance by an MB dealer.

I applaud your choice of the 124 coupe. IMO, the sedans are a dime a dozen today. A clean, well maintained (& preferably non smoker and garage kept) coupe is rare. In 1988 they only sold about 2,500 here in the US and the MSRP was 52-54K, (about 8k more than the 300E sedan) From there the price went up and unit sales down until they discontinured the platform.

From what I read here, the bottom end of these I6's is nearly bulletproof. The top end issues are discussed all over this forum. I suggest you read up on the M103 and M104 problem areas if you are not familiar with them. The dohc 24v M104 replaced the sohc 12v103 in the early 90's, which is apparently the time frame (or the particular vehicle) you are focusing on. They each had their problems with OEM failures, and knowing what they were will help you in analyzing vehicle maintenance.

If you are looking at an AMG coupe, expect harder than normal wear and focus even that much more on maintenance history.

FWIW, I expect my bone stock garnet '88ce (now with 74k on the clock) to be the last car I own. I'll leave it to my oldest daughter when I die.

Final thought (Wish I'd said that): There's nothing more expensive than a cheap Mercedes.

Good Luck