Real estate appraisal is a process by which the value of real estate is estimated, be it a home, a commercial premises, a piece of land, among others. 

This process is essential to determine the fair price of a property at a specific time, being very useful in real estate transactions and mortgage financing. 

However, a real estate appraisal can be unreliable when appraisers do not have transactional data and rely on inadequate methods to value real estate, especially commercial properties.

There are several methods to carry out a real estate appraisal, among which the comparable method, the income method and the replacement method stand out. One of the most used is the comparables method, which consists of comparing the property in question with other similar ones that have recently been sold in the same area. 

However, this method can be unreliable if it is based on prices requested on real estate portals instead of actual transaction prices. For example, if an appraiser uses asking prices from ads posted more than a year ago on real estate portals, it is likely that these prices do not reflect the reality of the current market. 

Asking prices do not always match actual sales prices, as they may be inflated by owner expectations or may not have been updated based on changing market conditions.

In this sense, it is essential that appraisers have transactional data, that is, information on real prices of recent real estate transactions in the area where the property is located. 

In this way, they will be able to make a more precise valuation in line with the reality of the market. The expected cash flow method, also known as the CAP rate, is especially useful for valuing commercial real estate, since it is based on the income generated by the property and not just on comparables. 

However, this method is not usually applied in Peru, which can lead to uninformative valuations from the investor’s point of view.