How to use a Verizon iPhone 5 on Sprint?

My cousin is getting the S4 next month, and he's willing to let me buy his iPhone 5 off of him. But I have sprint. I've still got a year left in my contract, but I want to activate the iPhone I plan in buying off of him. How do I do it? And I know it can be done, I've got a friend who has done it, but he's in Iceland at he moment. Do I just put in a sprint sim card? It's already unlocked, and won't be locked to a contract.

I couldn't find anything online that says you can do it, but I did find more sources that say you *can't* do it.

I thought it might be different with the iPhone 5, since because it's 4G/LTE it's the first iPhone where every carrier's version has a SIM card (in the past, Verizon and Sprint iPhones didn't all have SIM cards, and those that did, only enabled it for when you were outside the USA).

But the Verizon iPhone 5 SIM slot *is* sort-of unlocked, to the extent that you could install a SIM from AT&T or T-Mobile, and voice and texting would work, but probably not data. It would be the same if you were outside the USA and put in a SIM from whatever country you were in.

However, I'm pretty sure it won't work at all with a Sprint SIM. You could always try it; it wouldn't break anything.

P.S. Whether a phone is locked or not has nothing to do with whether the phone's in a contract. The phone doesn't "know" whether it's in a contract. If a phone uses only a SIM card (which the iPhone 5 does), then the thing that identifies the phone to the network is only the SIM card, not the phone at all (this is different from older Sprint and Verizon phones where the phone's built-in ID was what was recognized and matched to a number).