There are two parts to this project:
1) Membership site where users sign up and purchase slots on WordPress pages where they can add their links and associated text. User will browse or search for WordPress pages that he would like to place a link on. Each link will be displayed on the WordPress page of the user's choosing. We will also need PayPal subscription integration (including IPN functionality). We will need an admin area to manage users, manage which WordPress pages are available to users, and view PayPal payments.
2) Script, plugin, or php include to add to the WordPress blog or template that would would check with the membership site and display the user's link. If a user cancelled his subscription, his link would stop appearing on the WordPress page. The script, plugin, or php include needs to be the same code for all WordPress blogs (or templates), so that the WordPress admin does not have to customize it for each page on the blog.