You can now take advantage of In App Purchasing capability from within free applications, including free applications you’re already offering as well as new ones you may create. With In App Purchase in your free apps you can sell content, subscriptions, and digital services.
Here are some helpful tips to keep in mind as you design your app:
Deliver only digital goods or services within your app. You may not use In App Purchase to sell real-world goods and services.
Make your In App Purchase items available to all of the devices registered to a user. (The one exception to this is consumable items—e.g., virtual poker chips, in-game ammunition—that are used up or disappear after use.)
Be certain that the items you offer for purchase do not contain, or relate to, pornography, hate speech, defamation, or gambling (simulated gambling is acceptable).
Make sure that your free app is an actual application, not merely a demo advertisement. It needs to do something useful, interesting or entertaining.
Don’t set time limits on any of the functionality of your app, either for run times or life times. Applications that only run for a set number of minutes per session, or that expire altogether after some period of time, don’t recruit customers so much as leave a bad taste in their mouths.
If you’ve never offered a paid app, you’ll need to start by requesting a Paid Applications Agreement and setting up your banking and tax forms in iTunes Connect. Visit the Prepare for App Submission page on the App Store Resource Center for more details.