After playing with my permissions I have got things working as I want but I have seen one bug.
I have both the membership and classified plugin on my site.
I have the my classified page and classified page as a negative rule but when you click on the classified link there is a brief moment where it says "you are being redirected please wait" during these brief 2 seconds you can quickly click on the create add link and create an add.
The classified checkout page is also a negative rule and after posting your add you are taken to the protected content page.
However the add does get posted.