More often than not, the guns I buy from an ODTer has previous ODT ownership associated with it. I have 4-5 I can trace back to like 4 previous ODT owners. No BOS, just cash on the barrel head!
I always bring a little something to a free meet up. Ammo usually works; then it becomes a trade and both parties walk away with something including true positive feedback.
I have just said here, take it and give me something. No complaints about what I get in return and generally has worked out. Mostly face to face with friends, neighbors so not sure how it would work out here. I did one trade like that and it was fun. Turned out okay. I check WTB every day or so.