Starting an 8yr old

I was looking for tips at starting my 8yr old with MX. He was interested in a 4-wheeler but when he learned that there wasn't much competition in 4-wheeling he leaned more towards the bikes. Where are the websites and such for good youth info?

Of course we picked him up some riding gear at a garage sale (hey, not everone can buy new stuff to start with

) and are currently looking for a starter bike. He is 8 and about 49" tall. He fits just right on a 49cc but I think he'll outgrow that by the end of the summer. The 70cc we looked at was just a touch big but he could still put his feet on the ground. I figured that would be good to learn on. His best friend just got a 70cc from Pep Boys and that's what he wants to get. Don't laugh, it's actually a pretty decent bike and he's not looking to enter any competitions right now with it anyway.... it is, after all, something to learn on.

Any suggestions you all could give me would be great.

-Jared