Once known as “Surf City” Santa Cruz is home to a moderate climate, the natural beauty of its coastline, redwood forests, alternative community lifestyles, and socially liberal leanings makes Santa Cruz an ideal place to pursue the tiny-living movement.
As for regulations for the construction of second units/ accessory dwellings in Santa Cruz, they are classified into two categories of urban or rural. Urban second units are located within the the Urban Services Line while the Rural second units are located outside the Urban Services Line. Furthermore within these two classification of Urban and Rural there is another sub-divider of being attached to a public sewer or without a public sewer. After this level of segregation, the size of you secondary unit/ accessory dwelling depends on your certified parcel square footage/acreage calculation prepared by a licensed Civil Engineer or Land Surveyor.
Further information can be found here at the county of Santa Cruz or this link.