Alamo Heights, Monte Vista, or Olmos Park - Garage Apartments

[Kyle Handy]

I'm working with a client that is considering the idea of "house hacking" a home in the above titled areas as well as any other similar types of neighborhoods in SA.  They are wanting to find something nice that has a garage apartment or detached quarters that they could rent out to supplement the monthly payment.  Willing to spend between $300k-500k.  Does anyone know if these areas allow for this (I think, yes...) but more importantly what minimum requirements would this detached space need to be considered "rentable".  Thanks.  *Bonus question, what other neighborhoods should I look at for similar level of properties that may offer these types of homes?  Castle Hills?