The economy is in the hole, and real estate is in an even deeper hole. What better time to invest in a real estate search engine? Shasta Ventures just led an $8 million series B financing in Roost, a real-estate search engine that is grabbing data from MLS listings (actually from something called the IDX, or Internet Data Exchange, which is a close proxy to MLS listings).

As a result, Roost claims to have more comprehensive and accurate listings in the cities it covers than competing real-estate search engines such as Trulia and Zillow. Roost offers 3.1 million listings in about 30 major metro areas.

Yet Roost’s traffic barely registers. It is much smaller than Trulia, Zillow, or Redfin (which I’ve charted as a comparison below because Redfin also is not yet nationwide). Roost was late to market, so it is a bit surprising that it was able to raise a second round in this environment. Direct access to the MLS listings is an advantage, but is it enough to get Roost over the hump?

Roost raised 5.5 million last January from General Catalyst Partners, the Cross Country Group and Geolo Capital. They all participated in the current round as well. Roost also just added foreclosure listings from First American CoreLogic, a pretty common feature on real-estate sites.

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But just how comprehensive are these sites, and how accurate are their listings? Trulia offers 3.5 million listings nationwide, and Zillow has 3.1 million. But people look for houses in local markets, not nationwide. What matters is comprehensiveness withing local market

A few hours after I put up that post, I heard from Roost, a competitor to both Trulia and Zillow (with only 1.4 million listings in the markets it covers) that differentiates itself by getting its data directly from the same Multiple Listing Services (MLSs) that real estate brokers use. They just happened to have study in their back pocket (which they commissioned and paid for) that compares the “accuracy” of search results in three cities (Dallas, Miami, and San Diego) across different real-estate search services (Roost, Zillow, Trulia, Yahoo, and Google). The study, which was done by real-estate industry consultants the WAV Group, defines accuracy as the percentage of listing results that match listings the MLS for that city.

The results are in the chart above and, not surprisingly, Roost comes out looking great. For each city, it returns between 95 and 99 percent of the listings in the MLS. Trulia’s accuracy in the study ranges between a pitiful 9 percent for San Diego to 61 percent for Miami. (Zillow generally does worse across the board, with its accuracy ranging between 12 percent and 36 percent across the three cities).

Trulia disputes these results. Heather Fernandez, vice president of marketing, says:

The data looks very questionable, and not in line with our internal coverage data. Our data shows that we have roughly 70% coverage in most major metros.

And indeed, if you do a search for homes for sale in San Diego on Trulia, you get 4,395 results, compared to 6,036 on Roost. That’s 73 percent. (Zillow claims 7,661 listings in the San Diego city limits). Even if half of them are stale listings or not accurate in some other way, it’s hard to get to the 9 percent that the Roost-financed study claims. That’s because for some reason, the WAV study only compared homes in each city with exactly 3 bedrooms and 2 baths, within a $50,000 price range.

That methodology seems random and flawed to me. Would Trulia’s accuracy be greater if the study had looked at homes in San Diego that cost $400,000 to $450,000 instead of $300,000 to $350,000? Comprehensiveness would have been a virtue in the study’s methodology as well as in what it was trying to measure.

Still 70 percent accuracy is not that great, and it doesn’t seem like Zillow is any better. If the MLS in any given city is the benchmark, both have a lot of work to do. And Trulia, for one, is striking deals with different MLSs to incorporate their data. But it only has 14 so far, out of about 900 nationwide. MLS-based sites like Roost and Redfin may have more listings in the markets they serve, but they don’t serve every market yet. For instance, in San Diego, Redfin tracks 6,300 homes for sale, better even than Roost. Yet neither has any listings in New York, and Redfin only has 473,000 listings total.

Yet Redfin CEO Glenn Kelman also balked at my earlier suggestion that either Trulia or Zillow are even close to comprehensive within any given market. In an e-mail to me, he said:

What got me was that almost any real estate site has more homes for sale than Trulia or Zillow.

Frenandez doesn’t think that having the most listings matters. She responds:

Listings are commoditized –there are dozens of sites that offer basic listing information in every city across the country. It’s not a competitive advantage for an Internet company.

What is more important, she says, is the filtering the site allows home buyers to do to help them make an informed decision. I’d say it’s both. Those filtering tools (heat maps, sales comps, local school info) are also becoming commodities. You want to cast your net as wide as possible before you filter down so you don’t miss out on that one house that fits all of your criteria.

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And while he isn’t an investor in Seattle-based real estate startup Redfin, I’m pretty sure he likes their business model. The company is doing its best to completely remove real estate agents and brokers (and their absurd fees) from at least half of a home sale. If you use them when you buy a home, they reimburse 2/3 of the broker fee to you, keeping 1/3 for themselves.

60 Minutes covered the company last May, which led to a surge in business. CEO Glenn Kelman told me today that, since launching in February 2006, they’ve been involved in 1,500 transactions and have reimbursed $12 million to customers. The average refund is $10,000. The company had 2007 revenues of $5 million, he says.

They’ve just launched a new version of the website that includes more frequent MLS updates and the ability to group home sales by neighborhood and download the data. They are also providing deeper data on homes currently on the market as well as historical sales (they compete with a number of other startups in search, including Zillow, Trulia and Roost).

If you want to use Redfin, check first to make sure they cover your geographic area, which include the San Francisco/Bay Area, San Diego, Orange County, LA, Seattle, Washington DC/Baltimore, and Boston. Chicago is coming soon.

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What makes Roost different is that, instead of trying to list all properties in the U.S. as Zillow or CyberHomes do, or take in feeds from individual real estate brokers as Trulia does, it is negotiating with Multiple Listing Services (MLSs) in each metro area to get a comprehensive set of houses on sale. Redfin also taps into the MLS. (The MLS is what real-estate brokers contributeto and use to find homes on the market, and up until recently MLS data was well-guarded from the Web). Roost launches with more than a dozen cities/MLSs, including Atlanta, Boston, Chicago, Dallas, Philadelphia, San Diego, and Washington, D.C. (Notably absent are San Francisco and New York).

Roost is a real-estate search engine with comprehensive for-sale listings in the markets it covers, including for-sale-by-owner listings (which it does not show side-by-side with MLS listings because of industry restrictions). You can see all the photos for a particular house without leaving the search engine, you can see results on a map, and there are sliders (for price, bedrooms, square feet, etc.) to tweak results. It is a pretty-straight-forward site without a lot of bells and whistles. “We are laser focused on search,” CEO Alex Chang tells me. “We are not doing valuations. We are not creating heat maps. We are doing high-performance search.”

On the back-end, Roost hosts a directory of real-estate broker sites and delivers search traffic to those sites based on a combination of natural results and paid search. “I send qualified traffic to the broker,” says Chang. “They are buying clicks from me.” That is the business model. But Chang is going to have to crow pretty loud to get noticed by prospective home-buyers who have many other real-estate search engines to choose from these days, and maybe less incentive to go house-hunting in the first place.

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