This isn't the best answer for pinside market, but here is what I do. You said 4 of the people were friends or past customers. I always call or text people I know before I list a game. I also tell all the people I buy and sell with to contact me when they are looking to buy or sell a game. I sell more games before I list them this way. You tell them you are going to list it, you put the word out, and trust me if they are serious they will stay in contact with you. Plus, because they have dealt with you before, there is trust in place already.