Prior to that group, they had an online community for teachers looking for lesson plans. That probably sounds pretty random, but it's crazy the type of communities you can build and rally people around. If it's something that you're passionate about yourself and you want to connect with others that have that same passion, then an online community is something you should definitely consider.
How much will you make? I think my best month with Google AdSense was almost $5,000 over the last ten years. That amazing month blew my mind since it was actually near the beginning of my blogging journey. When you go from making zero to $5,000 in a month, that will rock your world. For me, it also got me even more excited because I knew there were other ways to monetize.