I'm surprised people are putting emphasis on programming language. You can use frameworks to code in LUA or C# for either IOS or Android. As others have mentio

I'm surprised people are putting emphasis on programming language. You can use frameworks to code in LUA or C# for either IOS or Android. As others have mentioned, to compile for IOS you'll need a Mac. Personally I develop for Android, but use a Mac. My recommendation is to look at which devices your consumers (including you) have and go with it. Read as others commented regarding Amazon's annual fee vs. Android's one-time (lower) fee. The PO box comment is interesting, but only if you're going to sell your app or have in-app-purchases - free apps/ad-apps do not require any address.