ther's nothing wrong  with best friends becoming lovers, or the other way around. What may not be advisable is to become lovers without becoming friends.

Friendship is the best soil for the seed of love to sprout since no emotional attachment is still  involved.

However, if you feel uncomfortable becoming lovers with your best friend   tactfully tell him you treasure your friendship together  and becoming lovers may just spoil the fun.

Chronological age does not always indicate one's readiness to have a boyfriend. Maturity, responsibility, and emotional stability are the more important  things to consider  before going into a relationship.

Before getting involved of a boy/girl relationship, the best to do is is to concentrate first on your studies , Expand  your circle of male and female friends.

you can have boyfriend anytime you want but to have serious boyfriend i think 18 is the ideal age for that.