I've owned several examples of this camera over the years, mostly using them for reportage. They are solidly built and reasonably robust. The one area where I think you should take care is in the shutter mechanism. This is a 'roller blind' arrangement made of interlinked slats. These are more inclined to fail than the more common Leica-style fabric blind type shutter. Repairs (here at least) are expensive, so it is best to ensure that the camera body is in full working order before buying. (Or negotiate an appropriate price).
The other point to watch is the lens mount. They are a bit prone to damage if handled clumsily. The Contax and Nikon cameras I've owned (same lens mount) required the adjustment ring on the body to be set correctly before offering the lens up.
Don't forget that although Nikon and Contax shared the mount rings, the focussing is different so some lenses are not interchangeable.