Another idea that stops house flippers and is fair to everyone, is a lottery system.

House comes up for sale. Everyone who touches the Placard is assigned a single number, increasing until 24 hours has passed. Then one number in that range is drawn. They get mail saying they've won, plus an item. Go to the Placard again, where they present the item, and pay for the plot.

You still have a timer to stop the flippers, and nobody cares because again, you only go by one time to get your number. So there is no frustration over sitting and clicking, and losing to people who just run up at the end.

(I do agree, we need at least double the housing we have now, though.)