This question is related to the halachic concept of ani hamehapech b'charara, or tortious interference, which I happened to just come across in studying Mishnah Peah.
If one has been looking at a house and is ready to make an offer, and the agent tells him that someone else (who happens to also be Jewish) has already put in a bid that is likely to be accepted unless a better offer is made, is one halachically allowed to put in a competing bid?
I found this http://www.torah.org/advanced/business-halacha/5757/vol2no35.html which has a lot of information about the halacha of ani hamehapech b'charara. In regard to answer D, the second bidder would theoretically not be able to find a similar property for sale, at least in that community. In terms of answer E, the house is still publicly listed as for sale, but it's not as if the seller approached the second potential buyer, except for the seller's agent encouraging the offer once he expressed interest in making a bid.