A client sent me a link to a property he saw on Zillow he thought would be worth looking at. But I couldn't find the address in the MLS. My first thought was maybe it was a private sale but there was nothing in the tax database for this property. After a little bit more research it turns out the street name in the Zillow listing is completely wrong -- Zillow says "Kearny" but the property is actually on "Kirkham" -- on the opposite side of the city. And, it sold almost six months ago while Zillow says it's still active.
I know it seems like I'm picking on Zillow today but this is a potential problem for almost all of the web sites purporting to provide current and accurate listing information. Virtually all of the listing information comes from the local Multiple Listing Service. Zillow and others take that information on a periodic basis and load it into their own database, massage it, and then present it to the consumer. Some sites, like Zillow, allow people who claim to be owners or agents to modify property "facts" and to post for sale listings directly to their site. As far as I can tell there is very little vetting of such information or the identity of the person posting it.
Another reason why getting information directly from the MLS is your best bet for timeliness and accuracy. Don't get me wrong -- the MLS is not perfect but it does have strong self-correcting mechanisms from the membership and the association which includes imposing fines on the agent/broker if inaccurate information is allowed to remain.
4 years ago