Hmmm.. looks like a clean car. If you p/m the VIN number to me, I can run it to see what the warranty issues were with it. The 202 Chassis C-Class are actually fairly reliable. Common areas are suspension bushings and oil leaks. Head gaskets are prone to oil leaks most often externally (common on most all in-line Benz 6 cylinders) and can usually be driven indefinately like that. If the engine has been "washed" or is too clean, I'd recommend a long test drive then maybe go back to it in a day or two and scan the right side and the rear of the head/block area for any signs of oil.