That puts your total estimated budget between $60,000 and $95,000, depending on finish quality, structural needs, and whether plumbing (for the added bathroom) is extensive.

We are also seeing hundreds of hotel rooms being added at the same time, and STR building permits are still strong in the area.  

In your shoes I’d definitely connect with others in the San Diego area who’ve already done ADUs — their real numbers and lessons learned are gold.

The major thing with adding utilities is the city and if they will allow it.

I ask my cleaners to flag any damage, leaks, or safety issues during their visits—this doubles as oversight without adding extra trips.Consistency is key: regular walkthroughs catch problems early, and setting clear tenant expectations for shared spaces reduces complaints.

I'd also recommend adding a slight buffer for the rehab cost.

There seems to be wide-spread anti-landlord movements online flagging ads.

It is great adding these unique amenities but you must stay on top of them

But not as an ad. 

MyRental by CoreLogic is another reputable platform.That said, the real gold is in pairing the credit/background check with income verification from the source—not just a paystub or PDF.