I had a black C3 1980. Got it around 7 years ago and just sold it a month ago. Good looking car, but you have to remember they are old and require pretty consistent maintenance. Mine had an electrical draw that we could never find, the headlights always seemed to stop working (vacuum system), I stunk like gas every time I drove it. I got a bunch of work done before I sold it (brakes, gaskets, water pump etc) and in the coming year or two it would have probably needed another couple thousand for other work.
If your not buying a completely redone cream puff, just be aware that you will have maintenance cost to account for.