Zillow announced today that it will power Yahoo’s “for sale” listings, in much the same way that Cars.com powers Yahoo’s new and used cars listings. Zillow typically carries 4 million-plus listings. The announcement spearheads a slew of online real estate announcements prior to next week’s Inman Real Estate Connect conference (which I am attending).

The enhanced Yahoo and Zillow tie doesn’t achieve the “buy a slot” status of other Yahoo vertical outsourcing — it would have been too expensive for any of the major real estate portals — but it also goes well beyond the current Yahoo-Zillow relationship, which basically consists of Yahoo’s syndication of Zestimate home valuations. That has been in place since 2006.

Under the new deal, the two companies bring together the real estate Web sites that have the second (Zillow) and third (Yahoo) highest number of unique visitors, per comScore. The deal, which is symbiotic for both companies, shows how things have changed from five or six years ago, when Yahoo itself was seen as a major threat to use open Internet listings to dominate real estate advertising. Now, Yahoo is basically content leveraging its sales relationships with national brokerages, while Zillow focuses on the content and local accounts. Real estate remains highly profitable for Yahoo.

While Zillow listings won’t go up on Yahoo until later this year, the two companies are immediately coordinating their sales efforts. Zillow’s “Premier Agent” program will be extended to Yahoo Real Estate. Current Zillow advertisers will be offered the chance to extend their relationship to Yahoo. Additionally, Zillow’s local “Showcase Ads” and “Featured Listings” will automatically be extended to Yahoo, making it easier for both sites to reach a quorum of users. For Sale By Owner advertising will also appear on both sites. One thing that Yahoo doesn’t get is access to Zillow’s growing display business.