[UPDATE: April 2016. Apple has announced that they’ll stop offering iTunes allowances but existing allowances with balances will remain intact until used. Instead of iTunes allowances Apple recommends using iTunes Gift cards. ]
Do your kids have their owns iPhones, iPads or iPod Touches? Do you want them to be able to buy apps, music and other items from either the iTunes Store or the App Store? Do you want to avoid giving them your AppleID password which would give them unfettered access to buy things? If so, consider setting up a monthly iTunes allowance.
Allowances can range between $10-$50 per month. In order to setup an allowance your child will need to have his or her own AppleID account. Create an AppleID for your child if you need to. I believe your child must be 13 years old or older to have their own AppleID account. People often think that an AppleID account must have a credit card linked to it, but this is not the case. Read Apple’s article about how to setup an AppleID account without a credit card.
Since Apple frequently redesigns iTunes I won’t write step-by-step illustrated instructions. They’ll likely be out-dated very quickly or they won’t match what you see if you have an older version of iTunes on your Mac. Instead, please follow Apple’s instructions for setting up a monthly allowance. Apple’s instructions tell you how you can suspend or cancel the allowance.
[UPDATE: November 2017. Apple has discontinued this service and no longer offers instructions for its use.]