A trustworthy used listing separates cosmetic condition from operational condition. Finish wear may be harmless while a sticky control, decentered lens element, or inconsistent card slot is not.
For bodies, inspection should cover controls, sensor condition, card slots, ports, autofocus, stabilization, battery behavior, and shutter count where the manufacturer exposes it. For lenses, check glass, aperture operation, focus, stabilization, mount wear, and alignment.
Actual-item photographs and a written return or warranty policy remove ambiguity. The Camera Shop model is designed to preserve those details against the specific serial-numbered unit.