After AlexT responses to my posts on the issues with pay to join my recommendation is to not use the pay to join feature, it is poorly implemented and there is nothing stopping bots from hitting the form resulting in huge number of pending payments. Plus, one may risk having their PayPal account frozen; if something prevents the user from coming back and completing the form, they have paid but won't have an account they can sign into. The "user" may then file a complaint with PayPal about paying for a service they have not received.