well depending on how developed he is, ie. what size instrument he can hold, I would look into some of the fender starter kits.
Here's a link to something in the area that I'm talking about.
http://www.activemusician.com/item--EM.033-0900-146
make sure you get him a good teacher, and also don't spend too much money on instruments initially as taste and development change rapidly.
Easy,
Janek