How to activate your iPhone 4 that you bought from someone else?

I'm planning on buying an iPhone 4 from a girl I go to school with. My verizon contract isn't up until the summer. I was wondering if there was a way I could activate the iPhone before my contract was up.

Absolutely.

Verizon will transfer your wireless service from your old phone to the iPhone.

Doing so has no effect on your current contract.

Activation lock