It'd cost you more to buy owned HR's than to just pay the early termination fee after the first month of service. Especially if you buy more than one.
Trying to find a less expensive older receiver that was really owned? Like a needle in a haystack. So many people think they own it after paying the initial purchase cost that many of the ones for sale as 'owned' are lease boxes and directv wont activate someone elses lease box on your account. You can call directv with the receiverID and they'll tell you if its owned or leased, but it could get onerous once you go through 15-20+ receivers with them all being leased.
I think this will prove to be a problem for directv over the long haul. I sure wont be upgrading or adding any new receivers after my contract is up.