Thanks for your post. I understand you are inquiring if you have to be 18 or older to have a Sprint account under your name and the answer is "Yes". This is a requirement for Sprint post-paid service and a credit evaluation is required to establish service.
Sprint Social Care Team
do a search for change of ownership in the search bar... it should be this link
make sure both parties fill out whatever
if it's YOUR account and you want to create a seperate account under YOUR name that will be a problem
but if you want to simply move one phone from a share plan or something and make it it's own plan you can have a CSR do that in minutes.