175K-miles for top-end is about right, with most needing some attention 150-200K-miles. But, I've yet to see a 16V car that wasn't completely abused needing a complete engine.
I would look for a cared for example, maybe even travel a bit. Project cars can be much more trouble than they're worth.
Talk to the owner. Maybe it needs a top end. Then the price is right.
1998 C230 "Black Betty"