Sorry, no answers, just additional questions: @katendarcy Which plug in do you recommend or use for facilitating the payments?
In the front end I would like to display custome fields of paid users only. Still I want all users to see all custom profile fields when setting up their profiles so they see what they are missing when they have a free membership.
designodyssey: I found that role scoper helps to shape the user types and their capabilities. So the user role should be the key. In future there might be two or more categories of paid users.
I see there are a few more of you working on this, so any hints are appreciated.