Whenever I sell something, I make every effort to either repair what I know needs repair, or make full disclosure. If I'm selling online, I'll have close-up photos of whatever the defect is. It's the right way to do things.
For months I've been buying quadcopter drones or the camera/gimbals for them, repairing them, selling them on Ebay, and using the gains to add to my own quad copter kit.
I bought a damaged copter from a guy on a forum. He listed all of the extras that came with it, then said "here's what I know is wrong with it", and mentioned a couple of minor things. He was asking $600, and I gave him $600.
I got the thing yesterday, and it was a box of parts. There were many broken parts, including three smashed ones that would cost nearly $500 used to replace. He had them in Ziploc bags, so he obviously knew they were smashed. He didn't disclose that. There were other things wrong, too. There's no point in me trying to repair it, as I couldn't get $1100 for it, even with all of the extras. I'll just part it out and try to break even.
I sent him PM on that forum and told him that he should have mentioned those three parts when he was listing the things wrong with the copter. He replied that I bought it "as is", as if that justified him withholding very important information from the buyer.
I don't know how some people live with themselves.