When an appraiser analyzes a 1-4 unit income producing property - they will typically utilize the Income Approach to inform their opinion of value. This approach looks at the local rental market to determine what the market rent is. They will also use the Gross Rent Multiplier in the neighborhood to calculate a property value.
In this video I take a deep dive on two actual appraisals so you can see how this plays out in real life.
Did you miss my last video where I explained the three approaches that an appraiser uses? Watch it here: https://youtu.be/phnyPbh7Ud0