as long as said "kid" does his research, and is responsible enough to take care of the snake by himself, i don't see a problem. i guess i would throw some parameters down like...

-needs job. reptiles aren't cheap to care for. you have to buy the right husbandry supplies, feeders, and be able to pay for vet visits, ect.
-needs all family/ roommates to agree with owning reptiles.

thats all i can really think of right now. i have had my little cousins (6 and 8 yrs old) ask me if they can have a pet snake and i flat out told them know. these kids couldn't keep a fish alive, and have an attention span of a door knob. a snake would defiantly not last long in that house. not to mention my uncle isn't a fan of snakes. so my 2 parameters are broken right there.