You can call in to Care and they will tell you if the phone has been reported as lost or stolen. They have access to this database easily.
Unfortunately, there is a second database of whether that ESN is currently tied to a contract. If the phone is tied to a contract, it cannot be transferred until that contract ends or is terminated and there are no charges to the line. The only way for a rep to tell you if the phone is tied to a contract is to run the process of activating it on your account. If it is not tied, it will go through. If it is tied down, the activation will be denied.
Hmmmm.... this must be a carrier specific thing then. I am customer care for another carrier and when I check on an ESN for a customer one of two things happens - Either the device pops up that it's on the negative list (lost/stolen) and the esn is locked, or a table displays the owner(s) of the device with activation date and ending date the device was on the line, if applicable. I should think it wouldn't be that difficult for Sprint to check the status
rexcanis, That's incorrect, When you call in they will tell you if it's clean, Reported Lost, Stolen or tied to an account. They can/will tell you if you purchase it whether it can/cannot be activated. They don't need to try activating it to see if it's tied to an account.
levi4u is correct. I called into care this weekend to check a ESN and they said it was still on a account that isnt paid. So I told my friend.. dont buy it.