PayPal API and Recurring Payments Cart Development and User Permissions (PHP)

This is one area that I don't know much about, and I was wondering if I might be guided in the right direction.

I'm developing one site that I'd like to keep vB-free, but I have no idea how to manage user permissions based on whether or not their recurring PayPal payments are kept up-to-date.

I'm developing this site in PHP with MySQL, and hopefully some form of PayPal API that will allow me to do this.

This site will have several levels of users...Free Account, which will include access to the main function of this site, and then several paid accesses with other functions that will make my users' experience easier (More functions depending on which access level they've paid for).

I asked the question soon after I joined here whether or not people have used forum software for a purpose other than as a forum. This is one of those times that I'm considering it, if only because I can tap into a fully-functional permissions-based system that already handles PayPal payments, including one-time and recurring.

Watcha think? Should I develop this site from the ground-up, or should I modify vB? The latter is what I'm more comfortable with. The former is essentially free, but involved FAR more work, not only coding at the beginning, but updating over time.

 

Well, for now I've decided to go the vB route. Some people may be baffled by this, but my only other option would be something like Drupal, which, yes, is free, but I don't really like how it operates, and even after trying my damnedest to figure out its coding standards, I still have no clue. :o

While I could code the whole thing from scratch (with help from WebAssist's Super Suite), I think that updating down the line will be a pain in the butt, and I still have no idea of how I would link user permissions with eCart's PayPal API.

It's a little more expensive to use vB, but it's what I'm comfortable with ATM.

That, and we may have some issues come up with our primary client, and I need to generate some money as soon as possible. This is just the quickest and easiest path to take.