IOS – Signing into a different Apple ID for Media and Purchases

There are a couple of gotchas I'm aware of.

1. If you buy apps on both iTunes accounts, they all get listed together when updates become available, not just the ones on the account you're currently signed into. So if you click 'download all free updates' iTunes will only download the updates for the account which is signed in. This can be confusing because you've told it to download all free updates and it doesn't tell you why it hasn't downloaded the others.
2. If you have an Apple TV and you want to use Home Sharing, then you can only share the content for one account at a time.

Firstly, you must bear in mind that each In-App Purchase is uniquely associated with an Apple ID and that there are different In-App Purchase types:

• Consumable - You need to purchase these items every time you want them, and you can't download them again for free.
• Non-Consumable - You purchase these items one time, and you can transfer them to multiple devices authorized with the same iTunes Store account.
• Non-renewing Subscriptions - You can purchase these items again after the subscription period ends.
• Auto-Renewable Subscriptions - You can purchase these items with different renewal periods.

There are, therefore, differences in the way the availability of the product is handled.

As stated on Apple's iTunes Store: About In-App Purchases:

You can't sync or transfer non-renewing subscriptions and consumable In-App Purchase to another iOS device or Mac. You can transfer non-consumable In-App Purchases and auto-renewable subscriptions to another iOS device or Mac authorized with your iTunes Store account. For example, if you transfer a game from an iPhone to an iPod touch, only the game levels will sync, and the extra ammo and experience points won't transfer.