WASHINGTON, DC—Information and analytics provider CoStar Group Inc. said Tuesday that it had completed its acquisition of Apartments.com, first reported on GlobeSt.com a month ago. CoStar paid $585 million to acquire Apartments.com, an apartment rental marketplace, from Chicago-based Classified Ventures Inc. in an all-cash deal.

CoStar says the deal creates an online information and marketplace leader in the $2-trillion multifamily asset class. “We believe that the two companies now together are uniquely capable of providing invaluable new services to both apartment seekers and apartment owners,” says CoStar founder and CEO Andrew Florance. He adds that the acquisition “will lead to an even stronger platform for the company's future growth and to increased shareholder value.”

When the deal was announced on March 3, Florance said it would pair up CoStar's multifamily analytics with Apartments.com's marketplace for property managers and owners to target prospective renters. He said the deal was a logical follow-up to his company's 2012 buy of LoopNet, offering “cross-selling synergy, just like the LoopNet deal did.”

In the $2-trillion multifamily sector—described by Florance as “bigger than the office vertical, which is where we started many years ago”—CoStar has assembled what the company believes is the most comprehensive information source covering US apartment buildings. CoStar has information on 17 million apartment units and the properties containing them across the US, Florance said in March, including availabilities, rents, key contacts, comparable sales, photographs and building characteristics.

“We intend to draw on our deep experience with all of these marketplaces and leverage our management, technology, sales and marketing expertise to make this acquisition a success,” Florance said on a conference call last month. He expressed confidence that CoStar's real estate technology capabilities would help Apartments.com build “the industry's most compelling apartment rental destination on the web. Conversely, we also expect that CoStar's multifamily information and analytics solutions will strengthen as we gain valuable demand-side data from Apartments.”

Apartments.com now joins CoStar's existing marketplaces, including LoopNet, CityFeet and Showcase, which Florance said rank first, second and third most trafficked sites for commercial real estate in the US. There are also LandsofAmerica and LandAndFarm, which provide a marketplace for rural land and farm properties; and BizBuySell and BizQuest, which CoStar says rank first and second by traffic among marketplaces for small businesses for sale.

CoStar said Tuesday that the Apartments.com brand has significant value and plans to continue to keep and build on that brand going forward. “The Apartments.com brand is recognized by over 95% of apartment owners and used by millions of apartment searchers,” says Florance. “Our goal is to transform Apartments.com into the best consumer experience in the apartment space.”