The problem would be payments though since you probably don’t want the instance admins handling your payment info. Maybe it could work more like craigslist though where payment is up to the buyer and seller to figure out, but that has its own problems. It does seem like it would be useful though if there was a way to make it fairly safe
Which is honestly a good thing, it’s so much better than instructions that are like click here -> drag to the left -> open a three level deep menu -> check the box -> reopen that menu -> click go. Or even worse, instructions that are a video