How much would I have to pay?

So I'm going to be buying a new phone and I really want the Iphone. I have 100 dollars to spend per month since I'm only a teenager. With only 100 dollars and I bought an Iphone 5 what would I have to pay every month(my parents are with t mobile).So would I have enough money to pay every month because my parents don't want to pay. Please Help I don't know WHAT I'm DOING. Please explain the plans and payments and stuff to me Please

American phone plans are so confusing and expensive, in the uk one phone works on all carriers and the plans are simple and cheap

$100 a month would be enough with T-Mobile.

So that will work for you.