The variety of real property that appraisers are asked to review are nearly limitless. This is particularly true of commercial appraisers whose assignments may include appraising vacant land, office buildings, retail complexes, industrial properties, and special use buildings. Licensed and certified appraisers must be competent enough to perform any assignments they accept; however, no one appraiser is expected to be knowledgeable about every type of real estate in every location. Fortunately, there are clear guidelines for appraisers to follow to ensure their appraisals are always performed competently.