Try a local sports store that sells second hand gear!
You can get a great price for a used pair of skates and they will be already be broken in.
Plus when your son grows out of them, you can sell them back to the store!
I started playing hockey around 6 years ago, i'm a goalie and all the gear that I bought was second hand.
As I grew and my dad knew I was gonna stick to the sport he got me brand new gear of my own.
Since your son is only young, I would suggest putting him in power skating,
It will teach him the basics of skating (forward,backward,crossovers)
You can also register him in a local hockey league.
His age group is called "Novice"
Hope it works out!
:)