This is similar to creating videos for YouTube (and is normally the first stage before becoming a course creator), however of course you’re creating an entire course. https://www.udemy.com/ is one of the industry leaders for online courses with over 100,000 courses, in more or less every category thinkable, and over 50 million students. If you’re good at arts and crafts, speaking a second language, house repairs, gardening, cooking, teaching, or programming (or anything else) then you can create a course and teach others about it. Again, similar to other methods, once you have made the course, it is done – you will continue receiving passive income for as long as it sells for.