I wanted everyone to know a very important detail about the ESN checker. It checks that the ESN is with Sprint and that the phone model can be brought over to Ting. It does NOT check if the phone has a "bad esn".
I recently purchased a phone off craigslist. Before I made the deal I used the esn checker. It came back clear. I met the guy and bought the phone. I tried to BYOD and it wouldn't work. I called Sprint only to find out that the account holder was in collections and no way to activate it. I am bummed to say the least. I would have made more effort to activate it before handing over the cash if I knew the esn checker didn't check for bad esns. I am not writing this out of anger. It's a detail I didn't see anywhere and cost me $170. Life will go on. The guy says he will meet me tonight and give my money back. Maybe he does and maybe he doesn't. EIther way I'll just move on but I wanted others to know and not make the mistake I did.