Just a suggestion: If you want to sell courses to academics it might make sense to develop a way of sharing the wordpress based courses with LMS's such as Moodle, blackboard, etc. This is typically done with a process called LTI. http://developers.imsglobal.org/catalog.html With this model you create the course once and then sell LTI keys to provide access inside Moodle to your content. Then your wordpress site sends user/grade information to/from the LMS and Wordpress.
There are many many benefits to this. I could go into more detail if needed/wanted.
Just a suggestion.