Housing is a consumption good, an important savings vehicle, as well as a self-insurance mechanism for most households. Such investments typically require borrowing from banks and other financial institutions, leading to a large and significant mortgage market in most countries of the world. Therefore, a stable housing market with a sustainable growth trajectory is crucial in promoting consumer lifetime welfare, stimulating economic growth, as well as maintaining a healthy and stable financial system. Despite the prevalent practice of housing market regulations, there are many heavily debated questions yet remain unresolved. First, are these regulatory practices effective in achieving the original objectives? Second, are there any unintended consequences (or externalities)? Finally, are there alternative and better (regulatory) approaches? These questions form the central theme of this project. My co-authors and I exploit a unique policy measure in Singapore that differentially targeted second (or investment) homes to understand the effects and the transmission channel of a tightening policy in the mortgage market. We analyse the differential selection and treatment effects across synthetic cohorts of loans issued within adjacent time windows before and after the policy implementation and trace credit outcomes up to 18 months thereafter. We will study the effect of the credit tightening policy measure on the mortgage borrower default (or delinquency) behaviour.