Mainstay, a residential real estate data and workflow company, announced in mid-September 2026 that it had acquired Truelist, a Seattle startup that built an AI-powered listing platform for brokers and agents. Terms were not disclosed.
Mainstay announced the deal together with more than $18 million in new growth capital. It said it will use the money to expand from its base of large residential investors into brokerages, agents and smaller investors.
Truelist founder and chief executive Carey Armstrong is joining Mainstay as chief strategy officer. Mainstay said Truelist adds a listing data and workflow layer to its platform.
What Truelist built
Truelist was founded in 2024 and launched in 2025. Its software helps brokers and agents create, manage and distribute property listings across the many multiple listing services (MLS) that operate around the US.
Armstrong spent years in senior roles at Zillow, including as vice president of its Premier Agent business, which sells leads to agents. She also co-founded and served as chief operating officer of Tomo, a real estate fintech company.
Real Estate News described Truelist as a platform launched in 2025 by a former Zillow and Tomo executive, and said the purchase came as Mainstay tries to extend its residential real estate platform into the brokerage market.
“Mainstay and Truelist have been attacking the same broken system from different angles — Mainstay on behalf of investors, Truelist on behalf of brokers and agents. Joining forces means we stop duplicating effort and start compounding it.”
Why Mainstay is buying
Mainstay was carved out of Opendoor as an independent company in August 2024 and is based in San Francisco. It is led by chief executive and co-founder Dod Fraser, Opendoor's former president, with president J.D. Rasmussen and chief operating officer Michael Dulfer. It combines customer data with its own and external sources into a single record for each property, and handles workflows such as transaction execution, property taxes, homeowners associations and payments.
The company says it has facilitated more than $12 billion in residential transactions, executed more than 2 million automated workflows across more than 50,000 external portals and serves 95% of the 60 largest residential real estate investors. Truelist gives it a product aimed at the agents and brokers it now wants to reach.
"Mainstay and Truelist have been attacking the same broken system from different angles — Mainstay on behalf of investors, Truelist on behalf of brokers and agents," Armstrong said. "Joining forces means we stop duplicating effort and start compounding it."
Mainstay's plan
"Residential real estate is still run across an enormous number of disconnected systems, datasets, and manual workflows," said Dod Fraser, Mainstay's chief executive and co-founder. He said the company had spent years connecting data, decisions and execution for the largest residential investors, and that the new capital and Truelist would let it offer the same infrastructure to brokerages, agents and investors more widely.
Mainstay describes its product as an intelligent system of record for residential real estate, combining proprietary data, pricing intelligence and agentic automation across buying, owning and selling homes. Its founding team spent more than a decade building and operating property technology at scale before the Opendoor carve-out.
Armstrong's previous company, Tomo, raised a $40 million seed round, according to InforCapital.
The founders and the funding
Truelist's own funding has not been disclosed. Mainstay's new round included new investors Parker89, Stackpoint, Alpaca VC and FJ Labs, alongside existing backers Khosla Ventures, Era Ventures and Clocktower Technology Ventures.
Clelia Peters, managing partner of Era Ventures and a Mainstay board member, said both teams had built and run these systems at scale inside the industry's largest residential platforms, which she called unusual.
A busy market for real estate AI
The deal brings together alumni of two of the best-known US property technology companies, Opendoor and Zillow,, one focused on large investors and the other on the agents who list homes.
Mainstay has not said whether Truelist will continue as a separate product or be folded into its platform.
