I think a time limit would be better than a post count. Or maybe a combo like (just an example) two months and 20 posts. Or something like that. But I agree that we'll get a LOT of junk posts from people trying to get their post count higher if the requirement went by post count alone.

In an ideal world, it would be based on each individual. Each person has to ask permission to use the sale section and a staff person would look at that persons past posts, etc and decide if they should be granted access. But I understand that it's not feasible. It would take up more time for the mods/admin.