Unlocking Hidden Value in the Housing Market Through Assumable Mortgages

Written by:

Steve Marcinuk

Date:

15 Dec 2025

Share

Share via Facebook

Share via Linkedin

Share via X

Copy to clipboard

The U.S. housing market remains largely frozen as homeowners with low fixed-rate mortgages hold off on selling, unwilling to exchange their sub-4% loans for today’s much higher rates. Buyers, meanwhile, face diminished purchasing power and limited options. Andy Taylor, founder and CEO of RetroRate, believes a significant untapped inventory could help ease the gridlock: homes with assumable mortgages.

“Right now, 70% of all outstanding mortgages have a rate below 5%,” Taylor says. “There’s a high concentration of people who have really great loans.”

Taylor argues that the solution isn’t waiting for the Federal Reserve to cut rates. Instead, he points to the pool of assumable mortgages—loans that allow a buyer to take over the seller’s existing rate and terms—as a way to unlock inventory and affordability.

From Gaming to Housing Innovation

Taylor’s route to real estate technology began in an unexpected place: the gaming industry. He started as a programmer at Electronic Arts but soon realized he wanted to build something he actually used. After spending countless hours on Redfin’s early map-based real estate search, he sent in a job application and became one of the company’s first 150 employees. Over six years, Taylor advanced from product manager to overseeing Redfin’s consumer-facing development teams in Seattle and San Francisco.

He later founded Approved, a mortgage technology startup focused on streamlining the loan process before Rocket Mortgage became dominant. Approved was acquired by Credit Karma and became the foundation of its mortgage vertical, connecting millions of users to lenders via data-driven rate tables.

Discovering the Assumable Loan Opportunity

The idea for RetroRate took shape in 2022, when mortgage rates spiked and the lending business stalled. Taylor noticed an article in The Wall Street Journal about assumable mortgages—a rarely discussed feature that lets a homebuyer take over a seller’s existing loan. He found that the concept, while little known, could have a major impact.

“Effectively, it’s a way for a brand-new buyer to take over a seller’s home loan—you buy the mortgage with the house,” Taylor says.

The data revealed a substantial opportunity. Roughly 22% to 25% of mortgaged homes in the U.S. have an assumable loan, primarily because all government-backed loans—VA, FHA, and some USDA—include an assumability clause. With 70% of all mortgages carrying rates below 5%, the potential savings for buyers are significant.

Taylor and his co-founder began gathering data from a range of providers, cleaning and mapping it to identify where assumable loans are concentrated. “We took that data, processed it—because like all real estate data, it’s been touched by a thousand agents and county clerks—put it up on a map, and ran analysis. We said, ‘Gosh, this is really interesting.’”

Data Accuracy and Technical Hurdles

Building a reliable database of assumable mortgages proved more complex than Taylor expected. “When I first started out, I thought this was going to be an easy process,” he admits. “But you really have to clean it up pretty hard to make it useful.”

RetroRate now operates a network of APIs and data sources, with varying quality depending on the state. The company uses redundant sources and a waterfall model that assigns confidence scores for each property’s loan data.

“The moment an agent looks at it and says, ‘I know for a fact this home has a 4.25% rate and you’re showing 5.875%,’ they’re never going to trust you again,” Taylor says. “It really has to be clean and accurate right from the get-go.”

RetroRate’s platform analyzes criteria such as interest savings over the life of the loan and monthly payment differences compared to current rates. The company offers this information through an API that delivers detailed, property-specific loan data.

Targeting Real Estate Professionals, Not Consumers

While many proptech startups aim for direct-to-consumer adoption, RetroRate has focused on real estate professionals. Taylor explains that most consumers lack a deep understanding of mortgage mechanics, let alone the complexities of assumable loans.

“If they don’t know how a normal mortgage works, they certainly aren’t going to understand how an assumable loan works,” he says. “I can’t really explain it to Grandma over Thanksgiving dinner. She’s going to say, ‘I’ve never heard of that thing. That sounds like shenanigans.’”

Instead, RetroRate works with real estate agents and brokerages—industry insiders who can communicate the value of assumable loans to buyers and sellers. The company is integrating its data directly into Multiple Listing Services (MLS) to address a key visibility problem: most assumable loans are never flagged in listings because neither agents nor sellers realize they exist.

“The listing agent primarily doesn’t ask the seller whether they have an assumable loan, and honestly, the seller wouldn’t know if they had one if asked,” Taylor says. “So it never makes it into the MLS, which means it’s never syndicated out to broker feeds, which means it’s never on Redfin or Zillow.”

RetroRate’s MLS integration now flags properties with assumable loans as agents create listings, displaying the information prominently to help attract more buyers.

Overcoming Myths and Industry Resistance

A major hurdle remains: agent education. Many real estate professionals have outdated or incorrect beliefs about assumable mortgages, including that they are rare, slow, or not worth the effort. Taylor points to a recent transaction that closed in just 33 days to counter the idea that the process is cumbersome.

“If you’re a seller and you can get 5% more for your home, which is what most sellers get when they advertise it, or if you’re a buyer and you can save $1,500 a month, I’d say that’s a good boon,” Taylor says.

RetroRate addresses misconceptions through partnerships with large brokerages and educational webinars for agents. The company positions assumable loans as a way for agents to boost business at a time when transaction volumes remain low.

“We show them this is a way you can boost your business at a time when everyone wants purchase volume heading into 2026,” Taylor says.

Market Impact and Growth Plans

Taylor believes that expanding access to assumable mortgages could help break the housing market’s current deadlock, which is driven by the rate lock-in effect.

“We were thinking about ideas that can really unstick the market,” he explains. “Stop getting excited about 6.3% rates when there are 4% or lower rates out there right now.”

RetroRate spent 2023 and 2024 refining its platform, with 2025 focused on user adoption and 2026 targeted for national expansion. The company aims to partner with 10 of the 25 largest MLS systems and scale into every state beyond its current launch markets.

“It’s basically taking those things we know are working and that agents really love, and getting them into as many hands as possible,” Taylor says.

Growth will center on partnerships and agent education. “As more listing agents start to list them, they become more visible in the MLS and major portals. Therefore, there’s more awareness, which continues to drive additional demand. I think we’re going to see this start to snowball in 2026.”

Even if mortgage rates fall, Taylor expects the opportunity to persist. “Let’s say we get to 6% by the end of 2026—that means there’s still 80% of loans that have a better rate out there in the form of assumables.”

For an industry facing persistent inventory shortages and affordability barriers, RetroRate’s approach offers a practical way to leverage existing assets—unlocking value and mobility in a market that has been largely stuck.