Those unsustainable yuppie areas are not for sale to yuppies or for rent. Those simply are speculation and a way to park money where a good interest rate is expected in the long run. It is an investment where the interest rate is not payed by real residents in the future, It is speculation where the interest rate is payed by other investors who still think there will be eventually some baby boomers who can afford it. The old neighbourhoods are destroyed not because there is a demand from yuppies, but there is a demand by investors who chose to invest in real estate based on former experience. Which tells you how clever these people are, but they do not really expect the old stories to happen again. They simply expect they find less experienced investors before the bubble busts. It is a legal form of chain and avalanche system, so basically fraud.