[markbolyard]

This can all be done within vBulletin utilizing the subscriptions manager and usergroup permissions. Your forum would be set up as private, you would sell your memberships though the subscription manager. When a visitor purchases a subscription, their usergroup level is changed, granting them access to all forums (or the forums you prefer). This means you can actually have many forums and based on the subscription level, set it so they can see One forum prior to buying the membership, and then additional forums (or all forums) once they buy the membership. Subscriptions are based on time, so one could purchase a subscription for a day, a week, a month, year.... whatever you decide. As far as the test... that would require a custom modification, or simply a form that they would complete and email to you that would allow you to manually change their access level.

Hope that helps.