Hi kfish,
I would like to know more in detail what are the kind of pages you'll need. If its an aggregated page, we can use view module to create the view, then this module allows to set views permission based on lists of available permission in the drupal site. This solve your first sentence stating that user can view content after they have the permission (registered and permission granted).
I would also like to know the use case of registering user and grant access to them. Would it be something like user submit a form, and system admin verify the form and grant access manually, or it is granted automatically based on a set of code analysis/rules on user input data, or does it related to payment, ie: user pay, and access grated after payment receive.
I'm interested to work on this as this is an area I would loved to look into. However, if it deals with payment method, I might need to admit my lack of experience on that.
Hope to hear from you soon, and look forward to work for you!
Thanks
Best regards
JY