He could become the bad guy in the eyes of the community because he would be the leader of the project that affects their homes. Let's say Luke doesn't tell Owen and Owen accepts the offer, Luke would not only affect himself, Owen or the ABC company, but also the buyer of Owen's house. Luke could influence the potential buyer by selling him a property that he knows won't be worth much in the future. It can be considered an unethical way to sell someone a product that you know will decrease in value over time