Even if photography is what you do for a living, I think I can speak for many in that the motivation to create images isn't always necessarily tied with the intentions to make money out of each frame that's taken. There certainly isn't any fiscal gain from all of what I shoot but I'm convinced that dedicating time to personal projects can still have a significant impact not just in my development as a photographer but on my overall perspective on life.
The challenge I've heard from photographers wanting to commit to photo projects is all the same. They're unsure on what they should focus there attention to or what will come across as an appealing enough subject that will spark anyones interest.
Isa Leshko has shared 5 valuable points all of which in my opinion are guaranteed to give you a more refreshed perspective on how to choose photo projects with my favorite tip being "Make work that matters to you."
It's the equivalence of setting up a blog. You publish because you love the process and feel strong about the topics you write about and not necessarily because you want to strike it rich doing it. If the latter happens, it'll be a satisfying side effect.