My thesis focuses on economic research at the intersection of macroeconomics, finance, and real estate. The core of this work involves developing quantitative models for the housing and mortgage markets. Specifically, all three chapters are focused on understanding the consequences of policy interventions on the mortgage market and their effects on financial stability and welfare. To address these questions, I employ a combination of complex computational techniques and empirical analysis. In the first chapter, titled "Mortgage Choice and the Credit Guarantee'', I propose that the mortgage credit guarantee provided on agency mortgage-backed securities, such as those issued by Fannie Mae, Freddie Mac, and Ginnie Mae, plays a significant role in explaining the prevalence of fixed-rate mortgages in the United States. I argue that it is essential to consider the endogeneity of mortgage choice when assessing the credit guarantee's impact on financial stability and the overall welfare of the economy. I develop a general equilibrium model in which borrowers choose between fixed-rate mortgages (FRMs) and adjustable-rate mortgages (ARMs) provided by a constrained financial intermediary. The government provides credit guarantees for fixed-rate mortgages in exchange for a premium payment, commonly known as the guarantee fee, paid by the financial intermediary. Mortgages are modelled as long-term contracts, such that the intermediary prices the entire repayment structure of each contract ex-ante at the moment of origination. Relative to FRMs, ARMs typically have lower required payments during recessions, thereby generating less cyclical and lower default rates. In an economy without credit guarantees the convexity of the mortgage interest rate for FRMs, as a function of the borrower's leverage, is larger compared to that of the ARMs contract. As a result, borrowers choose 60% of ARMs due to the intermediary's pricing of credit risk exposure. When I calibrate my model to the US economy with the credit guarantee on FRMs, the interest rates for both mortgage contracts decrease. However, since FRMs' credit risk is no longer priced, FRM rates become insensitive to borrower leverage. Two results stand out: i) Around 70% of the outstanding mortgage balance consists of FRMs, as opposed to 40% in the model without the credit guarantee; and ii) the government insurance results in larger and riskier mortgage originations. Financial stability improves without guarantees. Compared to the economy without guarantees, mortgage default rates are higher, while intermediary equity, borrower consumption and house price volatility increase. In the second chapter I extend my research agenda on mortgage availability in the United States. While the literature has extensively studied the ex-ante consequences of introducing teaser-rate mortgages (TRMs) on the housing and mortgage markets, in this chapter, titled "Restricted Mortgage Offering in the Great Recession'', co-authored with Dick Oosthuizen, I focus on the ex-post consequences of limiting access to TRMs during the Great Recession. TRMs start with a low initial rate, with the expectation of a rate hike in the future. I developed a life-cycle general equilibrium model that incorporates housing, long-term mortgages, and the choice between FRMs and TRMs. My findings indicate that restricted contract choices amplified the decline in house prices by approximately 1% point and significantly increased foreclosure rates. Firstly, constrained buyers face difficulties accessing the mortgage market due to restrictions on mortgages with back-loaded payment structures. Additionally, existing teaser-rate mortgage holders are unable to refinance into new mortgages. Had there been no supply restrictions, the share of TRMs would have almost doubled during the crisis. In the third chapter, titled "Printing Away the Mortgages: Fiscal Inflation and the Post-Covid Housing Boom'', co-authored with Tim Landvoigt and William Diamond, we address the impact of fiscal and monetary policy on the housing and mortgage markets. Our goal is to theoretically and quantitatively analyze the impact of fiscal and monetary stimulus during and after the 2020 Covid recession on output, inflation, and house prices. We identify three distinct channels by which fiscal stimulus can reduce unemployment in a recession, only one of which causes inflation. The first two are well-studied and widely recognized: liquidity enhancement and redistribution. The third channel, which is the most novel and relevant channel on this research project, is that a fiscal stimulus causes future inflation after a recession only if future taxes are not raised enough to pay for the stimulus. This lack of future taxation requires debt to be inflated away instead. This inflation reduces the real value of outstanding mortgage debt, resulting in additional redistribution from savers to borrowers that causes a boom in house prices.