I guess the biggest problem is wiring harness issues on these mid nineties Benz
you need documentation showing harness has been replaced.( do a search to find out which years wiring harness is an issue ). Problems window regulators, fuel gauge readings, lower front ball joints, accessory belt tensioner. Many of these things were warranty issues that had occured early on in the cars life

MAA sensor in the intake seems to need replacement as the miles accumulate, part cost is about $325

Engines are strong - need proof of frequent oil changes - as the miles get near triiple digits as on all cars automatic transmissions become an issue. Mercedes is good at offering rebuilt units but is thousands of dollars.

If you dont work on the cars yourself, dealership repairs can be pricey, good independent repair shops are necessary do you know of any.

by 1998 side airbags are standard, build quality is good,

need to go through service documents, and see about taking vin to Mercedes dealer for warranty repair log. like all german brands some C's are psssessed with electrical gremlins.

If a particular car has not seen any extensive body damage, the extensive source of parts for these cars, mercedes road side service, make these cars a psssibilty for an eight nine or ten year old car.

But there are always Toyotas