For the past several years, housing affordability has been discussed as if it were a force of nature. Everyone agrees it is a problem, everyone studies it, and yet it often feels beyond reach, like something that can only be changed by sweeping legislation or a dramatic shift in interest rates. What feels different right now is that some of the most immediate levers are not theoretical at all. They are administrative. They do not require Congress, but rather decisions. And that is why debates...