Scott has hinted at the essential element.
You need to understand who is using Zillow and/or Trulia.
You must decide if are going to incubate or sort.
With this understanding you must make a business decision...chase vapors or implement the correct strategy for sorting out the duds. It's not rocket science.
You make no money chasing vapors.
You will make money with the proper self-selection mechanism.
Before you hand over your hard earned money, you would be WELL advised to run a shill through the process. This exercise will make clear what is smoke and what is real. Both Zillow and Trulia sales folk sell smoke. YOU MUST IDENTIFY WHAT IN THEIR SERVICE CAN BENEFIT YOU. It is not what they are selling. But, if you respond according to YOUR observation, you will generate the business from the segment you want. If you don't do this you will be spending way too much time responding to people who are unable, unqualified and will never be able to buy or sell. Be the buyer or seller you want to do business with and get the consumer experience. You will then see the fabric behind what others have written regarding the BEST way to leverage aggregate websites.
Best of success to you,
Annette Lawrence, Broker/Associate
Remax Realtec Group
Palm Harbor, FL