How much is an Iphone after eligibility to upgrade to one?

I have Verizon & I'm scheduled for an upgrade in February. But I was wondering how much an Iphone would be if you could upgrade to one?& what about data plan? I want the cheapest one.& what's the cheapest Iphone I could get? How much is a 4 & 4s? Would the 5 or any of them be free?

I'm not 100% sure on prices with regards to contracts, but I know that it is possible to receive a free iPhone 4S or iPhone 4 using one of the referral schemes around at the moment. I think the best website for giving advice on this is http://www.iphone-for-free.net/. They have information about how the schemes work and how to get a free iPhone

hope this helps.