Cost and appraisal of ADU or separate unit addition in San Diego

[Michael Ndjondo makadi]

Question to more experienced investors and/or appraisers especially those in San Diego 

I am currently working to complete the renovation of our first property which is one its kind since it is currently a SFH but the lot zoning permits for 2 more units. So the plan was submitted for the addition of 2 units to the city and has been pending since. I found out not long ago that there is this new regulation according to our architect that allows for addition of 2 ADUs. That got me thinking since I know that for ADU, the developer impact fees are eliminated and thus can save us over 20k. But what I don't know is the implication on the appraisal after completion. We're using BRRRR in order to keep buying and adding 2 units in the lot was one the biggest attraction of this deal. So my question is how are ADU treated compared to separate units when it comes to appraisal? As an investor, all I care about is ROI which mean I won't mind paying the extra permit fees if the separate units will generate a higher ROI compared to ADU. Is there any potential significant appraisal difference to warrant the extra permit fees for the separate units?