What if I dont have credit card?

Hey,

All I want to get is a free app for my iTouch, but it wont let me create an account without a credit card... I can get my parents to lend me their number, but I am not sure how the iTunes store works.

Are there any fees? Or can they only charge you if you actually click to buy something??

If I sign up with their mastercard, do I run the risk of being charged for something I didn't want to purchase??