After you have a contract to purchase a home and you are financing then your bank or mortgage company will order a home appraisal from a licensed home appraiser. This third party professional appraiser for Single-Family homes will most likely use the Sales Comparison Approach to appraise your new home.
The sales comparison approach is based primarily on the principle of substitution. This approach assumes a prudent individual will pay no more for a property than it would cost to purchase a comparable substitute property. The approach recognizes that a typical buyer will compare asking prices and seek to purchase the property that meets his or her wants and needs for the lowest cost. In developing the sales comparison approach, the appraiser attempts to interpret the actions of parties involved in the marketplace, including buyers, sellers, and investors.
Data is collected on recent sales of properties similar to the subject being valued, called “comparables”. Only SOLD properties may be used in an appraisal and determination of a property’s value, as they represent amounts actually paid or agreed upon for properties. Since comparable sales are not identical to the subject property, adjustments may be made for date of sale, location, style, amenities, square footage, site size, etc. The main idea is to simulate the price that would have been paid if each comparable sale were identical to the subject property. If the comparable is superior to the subject in a factor or aspect, then a downward adjustment is needed for that factor. Likewise, if the comparable is inferior to the subject in an aspect, then an upward adjustment for that aspect is needed. The adjustment is somewhat subjective and relies on the appraiser’s training and experience. From the analysis of the group of adjusted sales prices of the comparable sales, the appraiser selects an indicator of value that is representative of the subject property. It is possible for various appraisers to choose different indicator of value which ultimately will provide different property value.
Here are some additional links for Buyers.