The accessory units are not.  

Accessory dwelling units (ADUs) have become a source of income to help families remain in their homes while providing affordable housing to elderly, single-person households, and students.The following requirements must be met for an ADU: Owner OccupancyOwner must reside at the main house or in the ADUProperties where owner does not live on site must be rezoned to allow more than one dwelling unitPermitted Zoning DistrictsR-1, R-2, R-3, R-4, R-5, R-6, RM-4, RM-5, RM-6 and in multi-family districts up to a total of five (5) unitsSizeUp to 800 square feet or 50% of the size of main house (whichever is larger)Cannot exceed 1,600 square feetAll properties, regardless of main home size, can have an ADU of at least 800 square feetApplies to attached and detached ADUsBedroomsNo limit on number of bedroomsUtilitiesCan have separate utilities (meters) or can share meter with main houseHeightDetached ADUs = 2 stories and 25 feet in heightAttached ADUs = must comply with height limit restrictions for the underlying zoning districtSetbacksDetached ADUs = may be located 3 feet from side and rear property linesCannot have an eave overhangMust be fire ratedTo avoid above measures, setbacks from side and rear property lines must be 5 feetParkingOnly ADUs over 800 square feet require a dedicated off-street parking spaceHappy to Help :). and remember unlike many counties or cities San Antonio has an amazing city staff, they are very friendly and you can always do a walk in to ask questions.

I'm also beginning to develop a business around the design, construction, financing, and property managing Accessory Dwelling Units in the area. 

If I buy a single family, It would have to have a small accessory apartment, which I would live in and rent out the larger portion of the house. 

It is considered part of the accessory structure.

Smoking or vaping of any substance is forbidden in the rental, garage, or any outbuilding.

Would a duplex that effectively becomes a 4plex receive a favorable valuation or would it be considered an "accessory" and thus not be valued at what we put into it.

This is a very common question I receive, so I wanted to share the details here for others to learn from.Some Less Common Renovations:-ADU Build Out- Building an Accessory Dwelling Unit (ADU) from the ground up in the Denver Metro Area is an expensive and time-consuming process (costing over $200k and taking 2+ years to complete).

If they don't pre sell, we definitely stage (with our own staging furniture and accessories) all of the common rooms and the master bedroom.  

Should you move from the property or move your homestead exemption to another property any ADU automatically reverts to an "Accessory Structure;" which does not allow for living quarters.