Buying one from Apple is only 499. That means this deal is only fifty bucks cheaper but you don't get all the warranty and support coverage. Plus I am willing to bet ten million dollars that they are refurbs. You really want to buy someone else's problem? What is the return policy etc.? Not a great deal honestly. You will get burned by this. Just don't say that you weren't warned first.
Once you get the ipad you can check the warranty on apple.com using the serial number. A refurb will not have more than 90 days warranty.