Can you unlock a sprint iphone 4s with ios 6?

I want to buy my friends iphone 4s but its on sprint. I have verizon though would i be able to take it in to them and have them unlock it or activate it to my account or do i need it unlocked first? And how could i unlock it please help

As far as I'm aware you can unlock any phone by ringing up the carrier it's registered with, although it'll cost you, there's also unofficial websites that do it.

Call the serivce to unlock it.