For many Just For Fun would be Phase 2 after Phase 1: accumulate enough affluence that Phase 2 can be done in a typical high cost of living city and doesn't involve moving to a cabin or in with roommates.
I moved from Seattle to Kansas City to be closer to friends and family, and I'm building a strange thing: https://www.adama-platform.com/
I'm working on how to explain it, but I love doing it just for fun. I love optimizing and just making things. Even if Adama fails as a business, the key is that I am building the platform I want to use.