clear esn just means that you can use the phone on your account when you get it. each phone is identified by an esn and when you want to switch phones on your account, you call sprint and give them the esn of the phone you want to activate, its called an esn swap. so clear esn just means it isnt stolen or anything like that and that its ready for you to call and switch it to your line. the no contract thing is true for any phone that you pay full (or near full price

) for. if youre an existing customer you can switch to the phone without having to sign another contract or anything like that. hope that helps