I don’t think it will become a big problem on housing market. First this is talking about their working visa. Once they get a green card, they will have to wait for 5 years in order to start applying for their family members to come to the States that will take another 8-10 years. That is a long wait. Second, if they make $150000 a year already, it does not seem to be a problem buying a house right now or before, why wait. Besdies, i know that a lot of immigrants waiting for green cards already bought houses, including me, we do not have to wait until we get our green card to buy a house. Their coming or not may not cause a tremendous problem to the housing market in a short time, i am talking about 3-4 years. Not to worry.