The average real estate agent gives the homeowner a value for the house, which ensures that the homeowner gives that agent the listing. Period.
You can hire professional, independent appraisers who will research sales and give you a detailed analysis of value. This takes some time and costs hundreds of dollars.
Realistically, how much work can a real estate agent offering a “Free Market Analysis” afford to do? Maybe she spends a few minutes looking for other similar houses on the market or comparable recent sales. Maybe. The object of the real estate agent is to get the listing and get the house on the market and allow the market, through the eventual buyer, to set the true value. The incentive of the residential agent is not to establish value. Absurdity aside, the incentive is to get the listing.
Be aware that many listing agents try to outdo one another by padding and stuffing “Listing Presentation Packages” with lots of meaningless fluff.