The market is pretty widespread. You'd be surprised how much $$ parents are willing to spend on their kids, if you choose wisely.
Do a Google search on your geographic area and "Youth sports photography". Be prepared to be amazed at first the number of companies out there, and secondly, at the overall poor quality of what is being sold.
For the most part, the younger the kids are, the more money their parents are willing to spend, but this isn't always true. Also, the more affluent areas are more receptive, but again, this is not always the case. People love their kids, and they are hungry for quality photos of their kids, and this is independent of social or even economic situations.
I've been doin pro sports much longer than youth, it took a group of parents I know to get me to try and land local youth gigs. Dennis is right, the money can be very good depending on your market. There's at least 10 companies in this small surrounding area that have poor quality IMO, matter of fact I'll be havin my pic taken by one of them soon for a team I coach. Two years ago pro baseball was first and youth was secondary when my scheduling came up - now youth summer leagues is first because the money is good.
Of all the pro shooters I know that make a living out of photography ALL of them shoot youth & high school as well as pro baseball/hockey/football/etc. Making money as a pro sport freelancer sucks! You cannot make a great living off it (as already stated this is aside from guys who are working on salary for someone and freelances on the side). MANY pro shooters shoot from youth all the way up through the highest level. You can find me at a 5-6 year old game one day and a high level All-Star Game the next, and same goes for many others - Dennis is 100% right.

