How much would it cost for me to get an iPhone 4S?

I'm currently on my dad's plan under AT&T, I don't have an iPhone.

I want to switch to my mom's plan under Verizon. She has an iPhone 4 and she's been on her plan alone for about 8 months. She has unlimited data, texting and calling. How much would it be to add another line (I guess it would become a family plan?)? I would also want unlimited everything, would I have to pay for that? I how much is an iPhone 4S with a contract? Please help! I just need to know because I'm paying for all of this by myself

Why would you want such a horrible phone the Samsung galaxy s3 is way better baby love.