If you can prove your home had the accessory dwelling unit (ADU) prior to the 2001 adoption of the new UDC, you can be "grandfathered" in. 

. §141.0302 Accessory Dwelling Units and Junior Accessory Dwelling Units There's a couple other options that could have resulted in the same number, but the point is it isn't a secret or based on who you know at DSD, it's knowing the codes better than anyone else and knowing how to build one on another.

Can you rent out your basement or look to buy a duplex or build an accessory unit? 

@Erin T. the exact line in the updated ADU laws that @Dan Heuschele and @Eddie Torres is 65852.2(d)(2), which says "The local agency shall not deny an application for a permit to create an accessory dwelling unit due to the correction of nonconforming zoning conditions, building code violations, or unpermitted structures that do not present a threat to public health and safety and are not affected by the construction of the accessory dwelling unit."

AB 670 (New California law passed in August 2019) states: "any provision of a governing document, that effectivelyprohibits or unreasonably restricts the construction or use of an accessorydwelling unit or junior accessory dwelling unit on a lot zoned forsingle-family residential use that meets the above-described minimumstandards established for those units."

There are homes that have accessory dwelling units (ADU) or casitas already on the property.

At the beginning of 2018, California passed a state standard for Accessory Dwelling Units (ADUs). 

Cheaper options don't have the ability to overlap the nails like the rest of the roofing system, but nicer options (look up "GAF Timbertex") are built with the intention to 100% cover the ridge nails.While you got a dimensional roof (good), looks like materials got skimped skimped on top.It'll likely be fine, just keep an eye on the silicon.In the future, I'd pony up for the nice accessories (self healing underlayment) and go mid tier on shingles.

Owning here seems more like a fashion accessory than a living investment.East village is relatively hip and cheap, but you are stuck in the value trap.

One thing to consider when purchasing 2-4 unit multifamily here in San Diego and Properties with Accessory Dwelling Units (ADUs) is that financing starts to become problematic having a certain number of unpermitted units or ADUs..For example in that triplex you @Ben Capone mention, if there are 2 additional units which are unpermitted or even if the units are permitted as ADUs, there is a good chance that an appraiser may call it a 5 unit  multifamily property which would require commercial financing and residential financing would completely be out of the question....in alot of these scenarios, the investor is then forced to back out of the deal as commercial financing is a whole different beast than residential (1-4 units) and typically requires more than 25% down here in San Diego.