Sure they could show the property but they cannot ratify more than one offer. Sometimes, sellers will continue to show in hopes of getting a back up offer, which is a good thing to have as a seller if you think there is a reason that the first offer will fall out, ie. shaky financing. NYC practices real estate differently than the DC metro area. I would think your NY agent would be able to tell you the practices in that area. If you need a recommendation for a NY agent, let me know.