Sorry to hear your friend is gay. It must be tough on you. My brothers (yes, both of them) came out of the closet. My older brother who is 22 came out at 19 when he entered college and it was hard for him. My younger brother who is 15 at the moment, came out at 14 (recently that is).
It was hard for my parents, because now I'm the only one who can bring grandchildren to the family tree, but oh well. What if I was a lesbian? That would be bad...my parents feel like they failed at raising their children. When my younger bro came out they gave up on having more kids. I stand by them all the way though. It's just hard seeing my two brothers have two other boys over all the time. Yep, they are dating guys now.
Anyways, good luck.
Just support him as best as you can, that is all I can say.