In an ideal world it would be easy to determine the value of a 2-4 unit multifamily property. You'd just find three exact properties, located nearby that recently sold and then average their sale prices.
In reality it can be difficult to find properties that have the exact same characteristics. That's why appraisers will make several value adjustments.
These adjustments will vary by location and by appraiser.
If you want to be an expert multifamily investor, then take the time to review recent appraisals in your area so you can better understand what adjustments are reasonable and expected.
Also - check out my previous video on how appraisers use rental comps to value properties based on the Gross Rent Multiplier. https://youtu.be/H3NhbtfWJyA