The simple membership plugin can be integrated with the WP Affiliate Platform plugin so you can reward affiliates for sending members.
Step 1 (Install the Integration Addon Plugin)
Download and Install the WP Affiliate Platform Integration addon.
Step 2 (Configure a Payment Button)
Create a payment button from the payments menu of the Simple Membership plugin (It won’t work with your hosted PayPal button).
Step 3 (Keep the Main Plugins Active)
Simply keep the WP Affiliate Platform and the Simple Membership plugins active in your WordPress site.
The affiliate plugin will track all the referrals and give commission accordingly if a referred user pays for a membership.