We analyze a model of mortgage markets, housing tenure choice,
heterogeneous agents, and default with closed form solutions. We uncover
new insights which may inspire empirical work, and we ground already
established insights in a series of tractable expressions. Then we study
optimal loan‐to‐value (LTV) regulation and show that the choice of an LTV
cap should balance the opposing forces of access to homeownership and the
negative externalities associated with default. Homeownership
affordability concerns induce procyclical elements into optimal regulation
which attenuate the countercyclical regulation justified by the negative
default externalities.