Zoning in San Antonio

[Grant Garbo]

I have noticed that there are a few properties in San Antonio that have multiple addresses (duplexes or quads) and are built on SFH zoned properties.

Does anyone know how this is accomplished without rezoning. I found a SFH, zoned SHF that I believe could easily convert to duplex, but do not want to go about the rezoning process. Some quick research revealed that process to be incredibly arduous and expensive.

Does anyone know how other properties managed to become duplexes?  I am assuming they were grandfathered in.  Does anyone have any suggestions as to the best way to proceed regarding rezoning?