I thought about doing that this year. There's leagues all over the city and Western Hills is one I thought about but I did meet with the folks at White Settlement. As far as I know, it's commissioned sales. In fact nearly all leagues expect some income from your profits. Some even want money upfront and it is a LOT OF HARD WORK. These kids play ball several days a week and multiple teams. That's just the way it works from what I know about it. I don't know of any that will pay you to come out and be the photographer no matter how good you are. Let me know if you do...
I thought I would do on line sales but I'm not sure that's what they want either. Ideally, they would like to have prints available that day so be ready to spend money on paper, ink and a printer. I didn't sign up for it so I don't know how profitable it can be. I do feel like if we're going to be doing work like this we should be making some profit though.
I know some parents are there anyway with their digital cameras so maybe those are good enough.