Zillow is adding a new tool that could extend the real estate website's appeal beyond buyers and sellers of homes to renters and landlords.

The company is adding estimated rent prices to the more than 90 million U.S. homes and apartments listed on its site.

"Rent Zestimates" builds on the site's marquee feature, the home value estimates that it calls Zestimates. It also ties in to a rental listings business that Zillow started in late 2009, upping its competition with newspapers, Craigslist and other classified advertising services.

I guess they didn't like Restimates, Zent or Zentals.

Zillow included cautionary notes in its announcement, making it clear that it's only estimating rents.

It said the estimates "can be used as a starting point" for determining a home or apartment's monthly rent price. The estimates may help renters get a fair price before signing a lease, when used "in combination with additional market information on rentals."

There's no doubt some renters will haggle after a quick check of the estimates, and landlords will look to see if they might adjust rents.

Zillow is expecting repeat traffic; it noted that 70 percent of people who move each year are renters, according to a 2009 Census housing survey.

I'm guessing the biggest users will be fantasy real estate players. It gives them factoids to consider when they're imagining whether to rent or sell, buy and rent, or maybe rent a nicer place.

It's especially easy to play virtual landlord when you combine the rent estimates with other information that Zillow generates. You can get a quick idea of a property's value, mortgage payments and rent, to see if it pencils out as a rental.

"Buyers and renters are not exclusive categories -- many people are considering both options when shopping for a new home. Similarly, many would-be sellers in today's housing market are considering whether to become landlords rather than sell at a loss," Zillow Chief Executive Spencer Rascoff said in a release. "We created Rent Zestimates to empower people with information and data to make the right real estate decision for them."

Zillow, which was started in 2006 by veterans of Expedia and Microsoft, drew 16.8 million unique visitors in February.

Zental prices ... I mean Rent Zestimates .... will also be available on Zillow's mobile apps.

Here are a few screenshots provided by Zillow: