User Upgrades (Paid Subscriptions) is part of XF, you can use this functionality to 'promote' users to different groups once they have paid via PayPal, which would then have access to areas of the forum you have defined.
We do this for certain sections of our forum as part of club membership.
Hey guys, just a few more questions about the membership part for xenforo...
1) Are there other payments aloud other than just paypal?
2) If someone chooses "subscription to re-occur", will the money be taken automatically, or will that person have to approve it first?
3) If someones membership expires, will they receive an email saying it expired, and giving them an option to renew?