OK - serious answer here,
so you don't HAVE to pay the $100 annual fee to get started. You can install the Apple development suite and the additional iPhone dev kit. Both can be downloaded from the Mac and iPhone development centers -- AFTER you register.
Think of "deciding to develop an application" as "deciding to play a Mozart French Horn Concerto" when you have never touched a french horn. It takes some training, lots of practice --- and yes, even some artistic skill.
So, if you are serious, then you really have 2 choice:
1) take some classes in programming and get started.
2) partner up, either with someone who is a coder that will work with you, or pay someone to develop your idea.