Real estate appraisal, property valuation or land valuation is the process of developing an opinion of value, for real property (usually market value). Real estate transactions often require appraisals because they occur infrequently and every property is unique (especially their condition, a key factor in valuation), unlike corporate stocks, which are traded daily and are identical (thus a centralized Walrasian auction like a stock exchange is unrealistic). The location also plays a key role in valuation. However, since property cannot change location, it is often the upgrades or improvements to the home that can change its value. Appraisal reports form the basis for mortgage loans, settling estates and divorces, taxation, and so on. Sometimes an appraisal report is used to establish a sale price for a property.
These appraisers also perform valuations on commercial property ranging from single to multiple tenant office buildings, shopping centers, retail, industrial, malls, hospitals, health care facilities, warehouses, and hotels to multi-family apartment buildings, co-ops, senior housing, condominium developments, and even vacant land, agricultural, and golf courses.  Regardless of the property type or local zoning, they'll determine the highest and best use of the project and assess the value using the actual or projected cash flow from the property's rent roll and financial statements, using both cap rates for capitalizing year one net operating income (NOI) and discounted cash flow (DCF) of multiple future income streams.  If you're a commercial lender, investor, builder, contractor, architect, or agent, you'll want to use these appraisers to conduct a feasibility analysis of any income producing real estate project you may be considering.  They can also help consult on construction costs and projected absorption rates.  They generally produce a commercial narrative appraisal when engaged for any commercial assignment.