I buy and sell gear all the time, mostly on Craigslist and occasionally on Reverb and have always had good luck. Recently, I posted an older Tascam US 122 Interface for sale complete with the original box, manuals, software and cables. I was contacted by a guy who asked me to hold it for a couple of weeks while he did some research to find out if it was what he needed. After 2 weeks I re-posted only to be contacted by the same guy. He said he had done his research and the US 122 would meet his needs. We arrange to meet, he pays me and everything seems fine. The next day, he contacts me to say it doesn't work. I inform him that I test everything before I sell and nobody has ever accused me of selling something that didn't work. I suggest he read the manual, check the cables, make sure the drivers are properly installed and ask if he understands phantom power. He responds that he doesn't need my advice as he is a network engineer. After a couple of hours of texting back and forth, he informs me that he has finally realized that the interface is not compatible with his operating system and wants his money back. He says that in all his years of dealing on Craigslist this is the first time he purchased something that didn't work. I remind him that it does work and that according to his previous text, the issue is compatibility which he had plenty of time to research before I sold it to him. I finally decided to give him his money. I told him my reputation is worth more than what he paid. What would you have done?