I buy and sell through Facebook Marketplace, and various local Facebook groups. It continues to annoy me the way folks are so cavalier about keeping appointments/doing what they say they're going to do when I'm the one selling. They say they'll come look/buy and then don't show up. The make demands about what I'm selling, for more pictures, different angles, take it outside for a pic, can I deliver etc. I don't make my listings haphazard. I cover every angle, the description is complete, the photos are clear and not blurry (unlike many listings I browse for things I'm looking for!) and I make a specific note if the color is off in the photos, a closeup if there's a ding, stain, flaw of any kind. I could understand all these demands if I were selling an expensive item, but most of what I offer for sale are clothes, household items etc., no furniture or other higher ticket items...most things, with a few exceptions, for under $20.
They offer less, even when I specifically say in a post that the price is firm and I won't go lower which I do with some items. They've asked if they can come get the item now and give me the money for it when they get paid at the end of the week/in a few days/next paycheck. Riiiiiiiight.
I've learned, the hard way, not to hold an item for someone, because most of the time they just don't show up. The only way I'll hold something is if the person gives me the money up front. If I don't see the dollars in my Venmo or PayPal, I won't hold it. Until the item is paid for and gone, I have extremely low expectations that anyone will actually show up when they said no matter how sincere they sound.