There are three generally accepted approaches for deriving a property value in the appraisal process. They are the cost approach, sales comparison approach and the income approach. Each is described below:
The Cost Approach: The theory is that the value of a property can be estimated by summing the land value and the depreciated value of any improvements. The value of the improvements is either measured as reproduction cost minus depreciation or replacement cost minus depreciation. Reproduction refers to reproducing an exact replica. Replacement cost refers to the cost of building a house or other improvement which has the same utility, but using modern design, workmanship and materials. In practice, appraisers almost always use replacement cost and then deduct a factor for any functional dis-utility associated with the age of the subject property. The cost approach is often the only reliable approach when dealing with special use properties such as public assembly arenas, marinas, oil refineries and the like.
The Sales Comparison Approach: The sales comparison approach in a real estate appraisal 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 and measure the actions of parties involved in the marketplace, including buyers, sellers, and investors.
Data and valuation information are 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. Sources of comparable data include real estate publications, public records, buyers, sellers, real estate brokers and/or agents, appraisers, and so on. Important details of each comparable sale are described in the appraisal report. Since comparable sales aren't 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. 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.

The Income Approach: The income approach can utilize the capitalization method or the discounted cash flow method.
The income capitalization approach is often used to value commercial and investment properties. Because it is intended to directly reflect or model the expectations and behaviors of typical market participants, this approach is generally considered the most applicable valuation technique for income-producing properties, where sufficient market data exists.
In a commercial income-producing property this approach capitalizes an income stream into a value indication. This can be done using revenue multipliers or capitalization rates applied to a Net Operating Income (NOI). Usually, an NOI has been stabilized so as not to place too much weight on a very recent event. An example of this is an unleased building which, technically, has no NOI. A stabilized NOI would assume that the building is leased at a normal rate, and to usual occupancy levels. The Net Operating Income (NOI) is gross potential income (GPI), less vacancy and collection loss (= Effective Gross Income) less operating expenses (but excluding debt service, income taxes, and/or depreciation charges applied by accountants).
Alternatively, multiple years of net operating income can be valued by a discounted cash flow analysis (DCF) model. The DCF model is widely used to value larger and more expensive income-producing properties, such as large office towers or major shopping centres. This technique applies market-supported yields (or discount rates) to projected future cash flows (such as annual income figures and typically a lump reversion from the eventual sale of the property) to arrive at a present value indication.