I'm yearning for a 1DX but can't afford to buy a new one. I'm saving up to buy a used one sometime in the next few months but have heard about the AF problems with some of them, and wonder what is the best way to go about buying a used one. Is there a serial number series I should avoid? Any particular questions I should ask the person selling the camera? Anything to watch out for? I would very much appreciate any thoughts.


