I'm 16 and I don't really care about holw people are, its how mature you act that matters.
Also, in my experience I've found that game shops/pubs don't really care how old you are, as long as you've got money they'll serve you.
If you don't want to lose muscle then make sure you always have a bit of fat.
As for girlfriends calling, on my game they've only ever called when I've been near their house
Yeah but hardly any members can afford cars and they won't be used in the gang war, so theres not really any point in adding more.
As for weapons, I think there is a great selection available already
When you had to kill Salvatore the Mafia didn't exactly let you walk up to him and kill him.
Anyway, my favourite gang is the Yakuza. They have good weapons, a nice car and 2 cool leaders