W204 is pretty decent but has some issues.
Namely, make sure the transmission fluid is not a slurry, some the factory radiators were bad and mixed. New or rebuilt transmission required along with new radiator.
The below two are pk issues
The front sam will be messed up and junk swapped in pk and more than half the functions will be goofy or missing.
The key most probably will be cloned and that itself is dodgy as hell, bcoz if the clone is bad, the car may decide to divorce the key, then you are stuck.
In other issues, as usual the engine mounts will be worn like clockwork every 40,000 miles if the owner thinks it as “saportss gaddi”
The usual undercarriage check for rubber perishing is a necessity, bargain as required,
Just make sure the owner isnt “jurman gaddi mazboot hoti hai, Allah ka karam sirf aail chenj karte hain”
If he/she is, then walk away from the deal.