WASHINGTON, DC—Information and analytics provider CoStar Group Inc. said Monday it had agreed to acquire Apartments.com from Chicago-based Classified Ventures Inc. for $585 million in cash. During a conference call to discuss the pending acquisition, CoStar CEO Andrew C. Florance emphasized the synergies between his company’s platform and the online rental resource provided by Apartments.com.

The combination, Florance said Monday, will 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 $860-million buy of LoopNet in 2012, 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, said Florance, 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 Monday’s call. 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.”

When the deal closes, Apartments.com will join CoStar’s existing marketplaces, including LoopNet, CityFeet and Showcase, which Florance said Monday 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.

Separately, Sacramento-based McClatchy Co. said Monday it expected to receive a cash distribution of about $147 million from the Apartments.com sale, based on McClatchy’s 25.6% ownership of Classified Ventures, which launched Apartments.com in 1998. McClatchy’s partners in Classified Ventures are A. H. Belo Corp., Gannett Co. Inc., Tribune Co. and the Washington Post Co., which on Monday said they expect cash distributions of $18.9 million, $155 million, $160 million and $95 million, respectively, from the Apartments.com sale.