15 years old he wouldn't have any interest in a Uke, I was thinking if he was younger than that it would have been a good idea.
I think I was about 14 when I started learning, I was self taught in the days before Youtube, I bought a fucked up Spanish acoustic off a mate for £15, I had one book which was fucking shite, the back page was full of chord windows though, I just practiced them for hours on end, once I got them sussed then I figured out how to play Live Forever by Oasis