@Jesse Aizenstat that last paragraph you talked about was the most important part of your discussion and facts so far. I can talk a lot about how appraisers consider adus in Portland, but it sounds like it's a whole other ball game in Santa Barbara when it comes to the covenant. In my opinion, an owner occupied covenant should completely eliminate the income approach to value or using duplexes as comparables. Comparables are supposed to be properties that a potential buyer of the subject property would've considered purchasing as well, and vice versa. An investor who's looking at income property in Santa Barbara has no reason (unless for a specific investment niche) to be considering sfr w/adu properties as their main motivation is income stream.
In Portland, when I was appraising, I would consider duplexes. I have appraised a sfr w/adu as a single family home w/adu, utilizing a bank from for a single family home. I've also appraised a sfr w/adu on a 2-4 unit income property form as well. My reasoning for changing, was based on the specific context of the property that was being appraised. How would the market (potential buyers) look at the property? If that answer included, or was dominated by investors, I would really have to consider the income. ADUs are becoming much more common in our market, so it's possible now to complete an appraisal using strictly sfr w/adu properties as comparables. I had lunch with a realtor friend of mine today who lists a lot of infill new construction. We weren't talking about adus at all, but he said that he's seeing new construction with adus having the most success in the market right now. His thoughts are that the new construction market is completely flat and the adu gave builders an advantage on the market place.
Regarding your specific situation, as an investor minded person, 3K rent on 200K expense, in Santa Barbara seems really dang appealing.
Oh yeah, a little comment on the "0.50" comments about Santa Barbara....the reason your'e getting such a better return on your adu scenario versus a purchase scenario is because you're not factoring in land value. Land value for your adu is free as you already own the property.....purchases scenarios are having to buy the land as well as the income producing improvements.
I hope this helps
Oh yeah, @Mathew Wray gave a great recommendation to just contact an appraiser. I would go a step further and say you don't really need to get them out to your property. A good appraiser will know your location and zoning designation in their head and can probably just have a 5 minute conversation of how they would "pull comps" in your given scenario, which would give you a good idea of how they'll be considering the adu's income as it pertains to value adding potential.