Add-on Premium accounts

Hei everybody.
Need addon.
A User can buy permissions to the forum.
In admin panel i can attatch to the user a specail group after his payment.
Also i need a special page, there users can look for offers thay can buy. I can add new offers and write info about it.
Maybe a saw plugin - premium content or user. If u know - link me please.
Thanks 2all.