as a former goalie and the father of a goalie. I bought a lot of my kids stuff through ebay at first. kijiji is another spot to check.
The only things I bought new for him when he was young was skates and mask. The rest was all used.
I did that until bantam when he started to get particular about his equipment.
Buying used is best because it save your son the trouble of breaking stuff in.
Good luck.
My kid is 16, I have pads and gloves but I think your boy is a few years away yet from those.
P.S. my kid has been a goalie since 1st year Novice. Personally, I didnt mind. At least I was able to help him. I will say this to you....Its a tough position. Make sure that you son has lots of positive feedback, even on those nights where he gets lit up. And please make sure that your son has coaches that understand what it means to coach a goalie. Goalies are not targets!!!!! Goalie management is something that seems to allude most coaches. I have all my coaching certification, feel free to contact me anytime.