No matter which way you do it, it’s passive income—money you earn while you sleep because you put these products up for sale on your website and a customer can buy and download them any time of day or night, automatically. All you have to do is check the sales periodically to see what topics or types of products are selling best so you can make more of those.
A great way to come up with a business idea is to brainstorm about your existing skills. Focus on identifying the skills that are unique to you or that you particularly excel at. Evaluating your previous professional experiences should give you a hint. Think of instances in which you were able to provide value to the organization for which you worked: do you notice any trends?