Los Angeles ADU/Duplex Appraisal Issues

[Fahad Masud]

I'm looking into buying a single family residence and building a second unit as a duplex or ADU, but my lender and other posts online say that is very difficult to get a correct appraisal done for a 2 unit home. In some cases, the ADU isn't considered at all in the ARV for a property.

does anyone have any tips on how to get the appraisal to come in correctly ? This is the only thing preventing me from moving forward with this duplex/ADU plan