What You Need
First things first – to develop for the iPhone, you’ll need a Mac. Pretty much any Mac will do, as long as it’s powerful enough to run the latest version of the Mac OS, Mavericks. But if you’re looking to go the cheap route, you can pick up a Mac Mini for relatively cheap, and it works just fine for a development machine.
Next, you’ll need to get a copy of XCode, Apple’s IDE for iOS development. So if you haven’t already, register for a free account at the iPhone Dev Center and download a copy of Xcode from the Mac App Store.
If you’d like, you can sign up for the paid iPhone Developer Program that allows you to distribute your apps on the App Store, but if you just want to try out iOS development the free account works fine.
If you get serious about iOS development, you’ll probably want physical device(s) (iPhone 4/iPhone 5/iPod Touch/iPad) as well. It’s true that you can do a lot of testing with just the Simulator, but there are some APIs that don’t work on the Simulator, and you’ll need a physical device for performance testing.
That’s it – so if you haven’t already, grab a copy of XCode, fire it up, and continue on!