How much is should pay and from where I can find tools to develop for IPhone and IPad
Well... it's not really $99. It is $99 per year.

To start programming for the iPhone you need to :


Get a Mac (if you don't have one)
Download Xcode


You can use Xcode to develop your application and test it on the iPhone and iPad simulator which comes with Xcode.

If you want to be able to download the documentation and developer resources you need to:


register for an Apple Developer ID (free).


To be able to test your applications directly on physical iPhones/iPads and be able to publish them on the App Store you need to:


enroll into the iOS developer program ($99/year).


You can wait to enroll only when you are ready to properly test your application on the devices.