It's expensive to learn from your mistakes. Much cheaper to learn from my mistakes.
Last year I bought a film body from eBay. When I got it home I gave it a quick check over and thought it was alright.
When I picked it up and shot a few weeks back I learned that the shutter was sticking and un-useable at a number of speeds. It was way to late to go back to the eBay seller.
This week I bought a new camera from eBay. When it came in today I gave it a solid check over to make sure it was working like a new camera. I sent the film into the lab. If it doesn't work out I want to be right on top of it and get my money back.
I could post the photos but do you really want to see what my brick wall looks like?