Selling products with dedicated access is a great opportunity to increase your earnings: big companies like Udemy or Treehouse prove it, achieving a huge amount of sales volume with this business model. Their income is intended to grow considering the number of people looking for their products.
In a completely automatic way, you could offer your users a restricted and exclusive access to tailored information, like a course, a study plan, a sequence of e-books, or even premium services, etc.
