This is possibly the easiest and most flexible script you will find for member management and subscription billing, or anything related to user management (free or paid). Not only does it easily integrate with any existing site, but it can be used to create it's own stand alone store/website as well with it's inbuilt wysiwyg page builder. The membership software comes pre-integrated with PayPal, Clickbank, Payza, E-Gold, Bitpay, Authorize.net, and Stripe, and it is very easy to add additional processors. It also comes with a built in system for managing affiliates