If it is a c300 I would avoid it like a plague, the c and clk classes were the dodge neon of german cars, they were designed to be cheap and cheaply made so people who could not afford a mercedes could buy a mercedes, but much like the neon right as it is about paid off it will fall apart at the seems.
all mercedes are expensive to maintain, but the cheaper ones often by the end of 5 years cost soo much to maintain vs the value of the car it is not worth it. I have seen the cheaper mercedes with wheel bearings failing so bad wheels fall off at around 80k but never seen such with their better models, engines failing, transmissions failing, and despite being a low end car any repairs either need to be done at a mercedes dealer or someone who can access the security system as most parts with anything electric are tied to security, especially transmissions, seriously transmission theft must be a thing in germany or something because I have never seen it in the us nor has any company tied their transmission or injectors or throttle body to a security system where any changes require re coding the modules.
Oh and dipsticks are not a thing on a mercedes anymore if you like to check your fluids, they started doing it with transmissions where you needed a dealer tool, then they moved on to engines where there is no dipstick, you need the special tool just to make sure you have oil. Were it me I would pick the rav4, oh and the new volvos coming out stay away from those as well, some models you might end up spending 2+ grand for a headlight going out, because they use modules for the headlights with special leds designed to keep from blinding ongoing traffic, but they are bloody expensive when they do not work and usually require the entire module assembly with headlamps replaced.