I have buddypress, multisite and membership. My first concern is the integration to include marketpress and classifieds.
It is important that there is only one registration page and login page. Integration of account data we can focus on at a later time unless and where relevant. I believe short codes will handle most of that.
So if I understand correctly, by disabling registration, and using the PayPal single payments option I can effectively create a free enrollment and premium options. (bare in mind that I want to control how many sites a particular enrollment package allows. I understand or believe I understand that the prosites(supporter) integrates with the membership plugin.)
I need to also integrate a custom field into the PayPal forms. Please advise as to which php files in membership and marketpress should be edited. Via my own initial review the custom field is in use for the membership plugin. Please advise.