The Realtor MLS services are information-based systems designed to help agents and their clients access the data they need to safely and intelligently buy and sell homes. Online listing websites look a lot like the Realtor MLSs but are really nothing more than marketing systems for sellers and their agents.
Most MLS systems now export much of their data on homes for sale to publicly accessible web sites like Zillow and Redfin. These sites make it possible for you to conduct a home search on your own in a manner that was unimaginable years ago. Prior to the advent of these public MLS systems, it was simply impossible for buyers to obtain a systematic list of homes for sale without working through a real estate agent.
Access to Data, but Buyer Beware!
Access to this data can be a big convenience for home buyers if you use them right, but you need to understand that this data has been put on the web not as a service to home buyers but as a marketing device for home owners and for listing agents. As a consequence:
They don’t contain critical information that is available in the Realtor MLS systems that would be available to an agent representing you.
They are designed to put you in contact directly with the seller’s agent who is listing the property so that you lose the option of having an agent represent you in the purchase of the home you call about.
They are designed to provide the listing agent with your contact information so that they can continue to contact you later to keep marketing homes to you or marketing their services as buyer agents to help you through the home purchase process.
When using these systems, buyers need to be aware that they are swimming in shark-infested waters - so beware of the sharks.