I realize that iPhone is a really glamorous development platform right now, but what exactly is your motivation for wanting to develop apps? Is it for your own personal use (that's what 90% of the programs I make are for), or do you actually plan to give it out for free or for pay?
If for personal use, I recommend you look into creating web apps. They will run on iPhone and you can make them look and behave like a real app with a little jQuery and Photoshop work. You can actually read a good book on the subject for free here:
Building iPhone Apps with HTML, CSS, and JavaScript - OFPS - O'Reilly Media
If for distribution purposes, make sure you factor in the other costs. In fact, even if just for personal use you will need a Developer license which runs $99/year.