To do that, you have to harbor a few fundamental guiding principles in your mind. Today, if you're at all serious about generating a full-time income (and more) from your online activities, then you need to focus on passive income as opposed to active income. Sure, the active income will help you survive. That's the scarcity mentality at play. But it's the passive income ideas that will help you thrive.
This has become a popular business model for online entrepreneurs over the past several years, and will probably just continue to grow in popularity. The best thing about selling online courses is that once you do the up-front work in creating the course and setting up your marketing strategy, you can get paid over and over again for work you do once.