I've got a 96 c280 w/165k miles. Head gasket @ ~100-130k miles is a VERY common, and expensive problem. Look for one that has had it replaces already. Also the EGR tube (replaced mine at ~150k miles) is a bear and was fairly expensive.

The only other problems I've had are minor - MAF sensor (easy DIY) and lots of brittle/broken vac lines (also DIY friendly). A couple of minor fit-n-finish issues like the antenna mast - simple and cheap fixes.

Otherwise I've been quite happy with mine (I'm the original owner).

Overall, given you can pick one of these up for ~$4-5k right now I think they make EXCELLENT daily drivers.