I've attempted to purchase games in this manner previously and it has always ended poorly. The game is always revoked, because these are hacked accounts that will simply have their password changed and the "Home XBox" changed quickly. The only accounts that will not be recovered and revoked will be those inactive accounts, which are guaranteed to not have any of the newer games. At that point you could probably find whatever older games you want to play for a cheaper price than the account, and without all of then associated headaches.

Please do not purchase games like this, unless you only plan to play the game for a few hours within a couple of days and are prepared to be associated with this kind of malicious account hacking that may get your XBox/IP banned from Xbox Live.

The terms of service and disclaimers you provide are tremendous red-flags, you don't provide refunds, new accounts or assume any responsibility for what you are selling. If you really have had such tremendous luck with these accounts, then you should be willing to back that up with the willingness to refund; since it is such an unlikely circumstance or outcome, this should be a negligible cost that you soak up as the service provider. Basically, if you lose the game, oh well, not your problem. I also don't see the word "escrow" anywhere within your post, so where do you stand on that?