I, myself, am 15.

*Shock and awe*

If you want my opinion on what to get a fourteen-year-old who has both rock and folk tastes, I'd go with getting him a hollow or semi-hollow body electric. It might be a little more expensive, but it transposes for folk and rock easily. It also can be played without an amp and sound like an acoustic (if you ever actually did that). I, myself, want a semi-hollow or hollow body...But I have too many guitars and mandolins lying around as it is! My room is kinda small, so I am constantly getting it piled up. Gotta make room for some more instruments around for my obsession with banjos and fiddles. ;)

So, either get him an acoustic-electric, or some kind of hollow-body electric (Which is your best bet, if you ask me!).

DO NOT start him off with one or the other if he has both rock and folk tastes.

I have mainly folk tastes (Irish and Scottish), and I had to go over six months with the absolute torture of only having my brother's Squire to play traditional folk music! It was horrible!