The primary role of GSEs (Fannie Mae, Freddie Mac) is not to lend money but to act as enormous insurance companies. They publish specifications for 'conforming' mortgages and then sell insurance against the risk of non-payment, which standardizes the mortgage product for the entire downstream market.

Home ownership is reframed as a high-risk financial instrument, not a safe investment. A mortgage constitutes a 5-to-1 levered, highly concentrated, non-cash-flowing bet on the economic future of a single zip code, making it far riskier than a diversified public market portfolio.

An insight dating back to Benjamin Franklin—that land could be used as collateral to create currency—has scaled globally. Modern banks have increasingly shifted away from business lending to become primarily mortgage originators, making entire economies highly exposed to land prices.

A mortgage is not a monolithic loan but a collection of disaggregated risks, such as non-payment and servicing. The U.S. financial system has created separate markets for each risk, which are then sold to different buyers like government-sponsored entities and specialized servicing companies.

Zillow moved from an ad marketplace for mortgages to originating loans itself. This captures margin from a high-cost part of the transaction, but more importantly, it allows Zillow to control and integrate the entire process, solving the consumer pain of juggling multiple vendors and disjointed communication.

The administrative task of collecting mortgage payments is a separate component called a Mortgage Servicing Right (MSR). These MSRs are actively bought and sold, leading servicing to be consolidated among large, specialized firms. This is why the company you send your payment to often changes.

The primary function of mortgage securitization is to move long-term interest rate risk off bank balance sheets. Entities like pension funds, which have long-term liabilities and are less sensitive to short-term rate hikes, are better suited to hold these assets, creating a more stable financial system.

Most consumer fintech products—payments, personal loans, investing—are merely means to an end. The ultimate goal for most consumers is achieving generational wealth, which is fundamentally tied to homeownership. This reframes the entire fintech ecosystem as a funnel leading to the housing market.

Unlike manufacturing (limited by production lines) or services (limited by time), the business of money scales with almost no friction. Writing an $8 million mortgage takes the same effort as an $800,000 one, providing asymmetric upside.