I don't think you're too young to consider it but there's some points to think about.
Are you going to college or university (assuming you're from the UK), there's a big difference and from your age, I wasn't sure.
Who would be paying the bills? If you're at uni, then you can put money towards it but if you're not or don't have a part time job, would that mean he pays for everything? That's a very dangerous situation to be in and can cause you to easily be trapped
Do you trust this person with your life? Moving in, especially away from family, puts you in an extremely vulnerable position and you need to think if you feel comfortable with this