Dorchester Condominiums

While among the site's users are some very serious real estate professionals who pay for PropertyShark's more comprehensive search features, "It's quite obvious a large chunk of them are simply consumers who don't necessarily pay us anything," Slack said. "It's a great site for consumers in that you can do all sorts of things.

"You can find out if your potential landlord is a slumlord (based on violations at the building); you can find out how much a neighbor paid for a home or for a building. There is a voyeuristic element to it. We try to leave it as open as possible. We don't try to narrow down the focus to meet one particular profession's needs."

Haines built most of the features at the site from scratch, with the exception of an open-source mapping platform. PropertyShark is constantly adding features, Slack said, such as a new section of the site that allows condo developers to promote new projects.

PropertyShark is always hungry for new data sources, he said. "We are looking to work with complimentary services, and it needs to be value-added for our users." For example, a company that has information on property sites with toxic pollution could be a very useful partner for the site because it adds another layer of data for the site's users to pore over.

The company now has 10 full-time employees on its staff, and Slack said the user rate is growing about 2 percent per week. The site is expanding into new market areas, too, with its jaws set on Florida and California.

Already, PropertyShark has launched some data and tools for other areas in New York, as well as New Jersey, Los Angeles, parts of Florida, Austin, Baltimore, Boston, Dallas, Houston, Philadelphia, Seattle, and Washington, D.C., with other cities on the way.

In addition to gathering reams of data from a variety of sources, the PropertyShark staff has assembled a massive collection of building photographs around Manhattan. Haines said, "We definitely spent a lot of time and money pursuing the fancy techniques."

But after some experimentation, they found a decidedly low-tech solution worked the best -- snapping individual photos of individual buildings. And within the next month they say they will have photographed every building in Manhattan.

Some of the data sources for PropertyShark also rely on old-school techniques to record information -- Slack noted that some government offices are still heavily invested in paper and microfiche systems. "They have political and budgetary constrains," he said, and PropertyShark has been working to digitize some real estate documents to make the information more accessible to the general public. The company offers its information free to nonprofit agencies and also for city and state agencies that supply data.

One of the latest features added to PropertyShark is an automated valuation tool that generates a median price for comparable properties sold. The founders joke that while PropertyShark provides quite a mouthful of real estate information, it doesn't yet offer a "psychic evaluation model" to predict future home prices…but don't hold your breath.