Niches for creating your own apps? Or making niche apps for a client?

Since I was advocating client work in my previous post, I'll go with the latter. Start with what you love. As an example I love aviation. There's a lot of money in aviation (as well as a lot of debt). Companies and FBOs sometimes have very specific needs that could be solved with an app: scheduling, customer loyalty, logging, etc. Reach out, talk to them, tell that you love what they love, just see what happens.

Also I have absolutely no marketing training and create apps in an organization that I have no control over the clientele, which actually works out great for me.