Trulia is an aggregator of data. The Aggregation phenomenon is new and Aggregators only dowload data two or three timesper week. Teh real estate market changes hourly. Homes sell, are taken off the market, and open houses are cancelled because of this.
Trulia has relationships with some brokers, but not all brokers, so Trulia gets its data from a variety of places. As is true of all internet home searching, it is a source to get a picture of what is happening in general in the real estate market. It is not your best source to actually find a home to purchase.
If you are truly interested in purchasing, you will best use your time if you create a working relationship with a knowledgeable and full service real estate agent. Real estate agents, through their brokerages, have access to up to the minute, 100% complete data and many real estate agents have systems set up to find you the properites that best fit your needs.
I recommmend working with a Realtor (not all agents are Realtors) because they subscribe to a code of ethics. A CRS (Certified Residential Specialist) Realtor is a Designation achieved by only 4% of the Realtors, so if you find a CRS, you find an agent that has put time and expense into their professional career. A professional Realtor will even take you around in their car to see the best homes for you.
Also, if you decide you are ready to purchase, a full service agent will recommend great lenders. I recommend lenders who have gotten extra training as Mortgage Consultants.
Feel free to sign up at my web site for a search that will update you daily on houses that fit your parameters.