sprints rule of thumb is if you didnt purchase it from them they wont insure it. BUT.. a BIGGG BUT.. if you speak with the rigth person at sprint they may do it.. but their policay is not to do it for a phone you have not purchased thru them...

you can put it on your home insurance... others have done this in the past.

i recommend you get the ESN form the seller, hit up sprint and make sure the phone has no history on it. also you can ask them if you can purchase insurance for it. thats your 100% sure fire way of knowing...