I was very into photography as a hobby at one point (still am to some degree) and I even toyed with the idea that maybe this is something I could do professionally. But the reality is that I would have unlikely become a staff photographer for Life or National Geographic and would much more likely have ended up as the photographer for the college news service--who was actually quite good but mostly took photos of rich alums shaking hands with the president.

Everyone differs of course. But, in general, one good strategy is to do something that you like well enough most of the time, you're good at, pays well and use your spare time and money to pursue things you like as hobbies.