Automated Valuation Models, known as AVM's, or Comparable Sale Reports are basically databases that try to match up similar properties to give you an idea of the range of sales prices that has historically been recorded.
This information is limited to factual data, such as how big the house is, the number of rooms and bedrooms, age of the house, and distance surrounding the house. Some databases used historical information, taken from mostly county record data.
Some databases are collecting information from appraisal reports, where a property's physical characteristics are being verified by a real human being.
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