Check the seller, more than the camera on ebay.
I have purchased several cameras on ebay and the advice I would give is to check out how much the seller knows about the camera. I bought one that the seller said he didn't know much about this camera and it showed. It was a RB 67 Pro S and it had problems with the mirror staying up when you cocked the shutter. I did wish to send it back but we worked out a slight refund. After tripping the shutter about 50 times, it started working fine. I plan to get some repairs on it when I have the money, but I have used it and it takes great pics. Another RB67 Pro S I bought worked but had some problem with the double exposure not working. Later another problem developed and I had both of them fixed. I now figure any camera I buy on ebay will cost and extra amount for repairs. You can't expect the guy that is selling his late father in laws camera to know enough to check that the cable release works or that the shutter speeds are 100% accurate if he doesn't even know how to load film in the thing. However, if you are buying from a person that has used it for years then you should have a good chance of getting a good camera as long as they are honest. Most ebayers are. Ric.