Seattle-based real estate tech startup Truelist has been acquired by San Francisco-based Mainstay as part of an $18 million growth funding round aimed at expanding AI-powered tools across the residential property market.

Founded in 2024, Truelist built an AI-powered listing platform to help real estate brokers and agents manage, create, and distribute property listings across fragmented MLS systems.

Mainstay — which was carved out of Opendoor as an independent startup in August 2024 — operates an “intelligent system of record” that automates data and transactions across the residential real estate lifecycle, primarily serving major institutional investors.

Truelist founder and CEO Carey Armstrong brings a deep Seattle real estate tech background to Mainstay, where she will serve as chief strategy officer.

Armstrong spent seven years as vice president of Premier Agent at Zillow before co-founding real estate fintech Tomo in 2020, alongside former Zillow leader Greg Schwartz. That startup raised a $40 million seed round backed by high-profile investors, including former Trulia CEO Pete Flint and ex-Zillow chief executive Spencer Rascoff. Armstrong served as COO before launching Truelist four years later.

“I’m grateful to everyone who supported Truelist along the way, and especially to the team who put so much talent, care, and hard work into building,” Armstrong said on LinkedIn. “If you don’t know Mainstay yet, don’t worry, you will soon.”

For Mainstay, the deal allows the startup to expand beyond its core client base of large institutional investors into the broader market of brokerages, agents, and smaller property owners.

Mainstay is led by CEO Dod Fraser — the former president of Opendoor — alongside fellow Opendoor veterans J.D. Rasmussen and Michael Dulfer. The company’s new $18 million funding round was backed by investors including Khosla Ventures, Era Ventures, Parker89, Stackpoint, Alpaca VC, and FJ Labs.

Mainstay said it has facilitated more than $12 billion in real estate transactions and serves 95% of the 60 largest residential real estate investors. Financial terms of the acquisition were not disclosed.

“Joining forces means we stop duplicating effort and start compounding it,” Armstrong said in a statement. “I have enormous respect for what Dod and the team have built, and I’m excited about what we can do together.”