Appraisal for newly built ADU?

[Mark Doty]

Has anyone had experience with how ADUs are appraised? My consideration is to use a BRRRR model to purchase a SFR, then build an ADU/Companion Unit on the property. San Diego is a tough market for cash flow (initially) but adding units seems to be an effective way to overcome the rent ratio. However, I'm unsure how the addition of an ADU would impact the appraised value.

Do you have resources around this topic or know how appraisals are measured on ADUs, in CA, if know?  Thanks in advance for input on the topic!