I'm trying to charge user for posting for sale ad in certain forum, what's the best way to do that?
Thanks in advance.
Easiest way would be to offer a VIP membership and have a plugin like MySubsciptions automatically add them to that group. Only allow replies from other member-groups in that subforum.
Anyway to charge by per post instead of membership?
No nothing like that exists that I know of. Unless you edit the MySubscription plugin to redirect to the payment page then once payment is done the post is processed and posted. You could also request a custom plugin.