Sell Content Add-on
The Sell Content add-on allows you to sell access to the content field of posts / pages or custom post types. The add-on works by filtering out and replacing the content the users sees using appropriate templates. Post authors, administrators and those who have paid for the content will on the other hand see the content in it’s original and unaltered form.
This add-on requires you complete the setup steps in order to start working. If you are updating from an older version to 1.7+, you will also need to go and update your settings as your old ones are no longer valid once you update.