We're planning to add an accessory dwelling unit (ADU) to the existing duplex by merging the two parcels together. 

I'm in the process now of looking into Accessory dwelling units to maximize the duplex and still occupy. 

Also, owners have nice vehicles and spend extra on them like new chrome rims, fully tinted windows, and other dumb accessory stuff.

I currently live in Los Angeles and considering the following scenario:Buying a single family home with a detached garage across from an elementary schoolCurrently a 3 bed/1 bath but would add another bathroomI would hedge the front of the house for added privacyI would say it is a grade C neighborhood of Los AngelesConvert the garage to an Accessory Dwelling Unit (ADU)Live in the main house but will eventually move and rent out the main houseSchool is mediocre, 5/10 from GreatSchools.orgMy thought by being across from an elementary school is that I may come across long term tenants because the kids would go there from K-5th grade. 

Officially, it will be deemed an "attached accessory dwelling unit."

A SFH with a "mother-in-law" suite is somewhat common (those are more formally called "Accessory Dwelling Units" or ADUs) but the trick to making it successful is buying OFF MARKET.  

I will ask, if anyone has commercial/office space experience, are there any commodities or accessories that would make it more desireable for potential renters? 

That may be a better place to focus https://www.sanjoseca.gov/business/development-services-permit-center/accessory-dwelling-units-adus/adu-amnesty-programEvery SFH is now effectively a duplex (or a triplex) that would align with your strategy, without the headache of fees on converting an illegal unit.

Wanted to connect with BiggerPocket members who are located in San Jose and actively interested to build and invest in Accessory Dwelling Units (ADU) as an affordable rental option.

I was reading about The additional Dwelling Unit Pilot Program where you can add an accessory unit.