Iphone on Verizon Straight Talk?

I want to get the new Iphone 5 and i heard you can buy a phone and then bring it into Walmart and get it used on Straight Talk. I was wondering if i could just buy the iphone from the apple store or website then do it but would the actually phone cost more since its not a contract? And would it be cheaper to just go on a proivder like Verizon, Sprint, or At&t but to take consideration that i don't have plans on either of them, Also i want to have unlimited text, unlimited web/data, and like 300 mins of calls.

Its possible.
but straight talk data isn't unlimited, its 2gb, when you go over the shut off service.

Honestly a contract is your best bet. It will make the phone significantly cheaper. Ofc through the 2 year of the contract youll end up paying a little more than the phone price itself. You also get the text, data and minutes which will pretty much be more worthwhile. Unless your like me and buy all kind of phones on the market just to test them.