For example, I suddenly need to know a lot about tax because with my sudden increase in income I don't know what to do. I would easily pay $50 for a tax-for-dummies who make above $10k a month book. It's a small niche, but it is valuable.
Or healthcare. For sick people, this topic is very important. If there is something that offers me good value for this, I will pay for it.
I am asthmatic, for example. There are very few software out there to help asthmatics.
Don't do the adworse nonsense of years ago. Do tiny projects that help people or solve peoples problems and it will be easy to make your dollar.