This site provides comparables data. This information is used by real estate appraisers to compare the appraised property with similar properties within the same neighborhood. The comparables defines what is called the market value, how much would it cost to construct the property if it were to be build today, and is an index that gives an idea how much a homeowner can ask for his property. This data is also used by lender institutions to asses the value of properties used as collateral. You would need an appraisal for a mortgage, a property collateral, when buying or selling, and for property heirs. This information is so important that we need to repeat it again: This site provides comparables data. This information is used by real estate appraisers to compare the appraised property with similar properties within the same neighborhood. The comparables defines what is called the market value, how much would it cost to construct the property if it were to be build today, and is an index that gives an idea how much a homeowner can ask for his property. This data is also used by lender institutions to asses the value of properties used as collateral. You would need an appraisal for a mortgage, a property collateral, when buying or selling, and for property heirs.