I am shopping around for a used medium format Mamiya RB67 camera to broaden my horizons outside of the 'work' photography I do with my Canons. When I'm looking at a used body what are some specific things I need to look for in order to help me determine the condition of the camera? Are there any good resources you can recommend to help me determine more-or-less what the going rate for a camera so I can determine if a sellers asking price is fair?
I wish the Shutterbug Classifieds were still worth looking at. If you can find an old print edition in a library, it's worth a look -- their rating guide was pretty much the basis for the condition rating that retailers still use. Something rated at 8 or higher, for instance, can't have any mechanical or optical defects, and the cosmetic difficulties are restricted to that inevitable greying that the "lizard skin" acquires over the years and some minor brassing (the black paint or plating has worn through at the corners and in areas where you'd expect a lot of handling). Just about every brick-and-mortar photo retailer with a used department I've been to over the past twenty years or so sticks pretty close to the old Shutterbug guidelines.
One thing you do need to pay close attention to with the Mamiyas (and with the Fuji 6x8), though, is the bellows. IIRC, you have a bit of time with view cameras, so you should be aware of what to look for (pinholes, light leaks, etc.). Make sure the body and back mate properly whenever you buy a back. And if you have the ability to check the shutters in the lenses for timing, that would be extra cool, but you can usually check the longer times pretty accurately and "earball" the rest (and like any mechanical shutter, expect them to be a little slow, but not outrageously so. You can always make up the difference in the aperture if you're within less than a half-stop.)