The zoning key words you will want to look for are "Accessory Dwelling" or "Principal Building".

Which makes me wonder why here in Los Angeles there is an extreme housing shortage, rents are going through the roof, the state recently passed an law making Accessory Dwelling Units easier to build in an effort to mitigate the the housing shortage, property values are at a level at or above the housing bubble peak. 

@Michael Pursell following up on @Charlie MacPherson good comment you also may want to pay attention to the exact wording of this stuff and how its individually interpreted by the various building departments: Accessory Dwelling Unit, In-Law and other terms may mean something slightly different town by town and be treated differently, likewise if you owner occupy or not. 

Accessory apartments may be allowed, but often come with a requirement that the primary area of the residence is owner occupied.

One thing I will throw out is the new Accessory Dwelling Unit (ADU) Law that was passed in California, allowing you to rent out a 2nd unit even if its only zoned for 1 unit.

Then you can convert an existing structure or add a new Accessory dwelling unit on the property which can be rented for additional cash.All the choices have their pros and cons.

Conventional Manufactured 80% LTV/HCLTV/CLTVFHA VA USDA Manufactured.When a manufactured home has an accessory unit (mother in law, granny unit, guest house, etc...) the accessory unit will disqualify the manufactured home for financing.When a manufactured home is the accessory unit it will disqualify the property (technically Fannie / Freddie will allow, but investors do not).Very important -Accessory units are ONLY allowed/accepted, when the property is officially a "single family" property.

A judge won't be sympathetic because you are an accessory to a crime.

At one time, it was the prevalent trend for people to style their houses according to a certain template with one certain color palette and similar furnishings and accessories.

I called on retail bicycle stores to sell them bicycle parts and accessories.