Be very VERY careful with agencies. Do a lot of homework on the ones you do find.
Also remember modeling is fun, but sometimes can be too much for a little one, I know I was that kid. I was modeling at 10 and everyone told me I needed to have this that and the other thing done blah blah........messed with my self esteem.
On the other hand, it gave me a thicker skin, and I still model today.