You can post in any forum including the classifieds from the first post, up till your last.
We have no post count minimums here at all. You really should make a post in the classified under the non gun section for your hammers. And bump it every now and then to keep it near the top. There are lots of members here including me that will be more than happy to give you great reviews of your hammers and our level of trust with you.
As for becoming a supporting member, there should be a click box at the top of the page letting you becoming one.
You don't need to become a business advertiser unless your sole intention is to sell your products here in the classified section.
Any further questions, fell free to post here, or ask any of the mods in a PM.