We do sell to minors, but we do have to talk to the parents as well as the minor. We have a form that new-potential-owners fill out, and in the case of selling to a minor, the minor has to fill out the form, and the parent does as well. Doesn't matter if the minor is 17 and turning 18 in a month or if they're younger, this way, we know the parent has knowledge of chin care as well as the minor. We also talk to the parents about chin care and verify that the minor is allowed to have the chin, about temperature of the house, that kind of stuff. That way there's no surprise when someone young shows up with a chin one day.
It somewhat does depend on the teen. If someone comes to me talking about buying a chin and appears to be intelligent and mature, then we proceed with the above. But if I get an email or call from someone who's acting immature or asking me, well how can I hide the chin from my parents, how can I convince them? Like I have no problem giving information, but I'm not too fond of people trying to finagle their parents into letting them have a pet after the parents say no. But in that case, even if we did get to talking with the parents, that's typically when it would come out that the parents don't want the kid to have the chin... and when they say that, that's the end of it.
We have sold to families that have small children, like 9 or so I believe, but that chinchilla was being bought as a family pet, not a pet specifically for the 9 yr old (and the mom was going to take responsibility for all the care). The youngest I've sold a chin, where it's going to be the kid's pet, is 13, and I think that's a good age as the youngest I'd sell a chin to (with parental consent).