It looks like family members can’t add payment methods to their own settings in iOS. Only the family organizer can do that, rendering everyone in the family unable to buy anything without using a payment method provided by the organizer. What is the point of that? And more importantly, what’s the workaround?
iPhone 6s
Family members can buy/redeem iTunes Gift cards to the account. Charges will be deducted from the account balance before the organizer's credit card is charged.
App Store & iTunes Gift Cards by Email.
Family members can buy/redeem iTunes Gift cards to the account. Charges will be deducted from the account balance before the organizer's credit card is charged.
App Store & iTunes Gift Cards by Email.
There isn't a work around except to use a second Apple ID to make your own purchases.
Family members can’t add payment methods to their own settings in iOS
