One thing to keep in mind with buying used receivers..
A. Make sure the receiver has a card from an account in good order. If you get one that has a bunch of PPVs charged, or from an account that has a balance on it, you will be responsible for the balance before you can use the receiver.
B. you will still have to pay $25 to get the "old" card exchanged for a new one.. you send them the old card + $25, they send you a new card.. not sure what the costs are if you don't have a card at all, but I heard they are $$$.
*this is DTV, not sure about the dish.