I'm planning on getting the Moto G, I'm 17 and I don't know if there's a minimum legal age.
If you're planning on signing up with a particular cell service, you have to be an adult to sign a contract. In B.C. that's 18. However, I'm fairly certain that if you were to buy a prepaid phone from a store or gas station then you're technically not entering into a contract, so it shouldn't matter. It all depends on the local laws where you're at. I guess I could have been a bit more clever & looked @ur profile.GL