Selling digital course is profitable but creating a digital course is really hard. You might have a great idea for a course, you might even have teaching skills but to design a course by putting together course content is very difficult. Creating a digital course is very different from creating instructional videos and tutorial ebooks. To create a full-fledged course, you need to create lessons in videos, podcasts, ebooks, and infographics. Just because you know something does not mean you can easily create a digital course on that topic. For example, I have been doing social media marketing for a long time, I can teach how to market on social media. But creating a course for social media marketing is a different thing.