It’s common for audiophiles buy used gear
Audio dealers sell online all the time
We cannot control the behaviors of others including dishonest buyers. It’s the risk we all must bare. The alternative is to do nothing, then nothing will be accomplished. We accept the risk in order to move forward AND not live in fear.
Maybe sell to a dealer or business like TMR which would lower your risk, but at a cost- nobody works for free.
The OP seems overly fearful of getting burned when selling. The risk will always be there, but the fear is optional.