how old do i have to be to open an iTunes account?

Over 13, if you are under that then you will need to be part of family sharing and the family organiser can create an under-13 account : Family Sharing and Apple IDs for kids - Apple Support

Vaboobie,

If you are in the USA, here are the rules:

"Only persons age 13 years or older can create accounts. Accounts for persons under 13 years old can be created by a parent or legal guardian using Family Sharing or by an approved educational institution. Children under the age of majority should review this Agreement with their parent or guardian to ensure that the child and parent or legal guardian understand it."

Details, and rules for other countries, can be found at Apple Legal.