Sonoma Permit & Resource Management Department (PRMD) has a hotline re: zoning questions (707) 565-1900 option 9. With a property address or better, parcel number, they will be able to tell you what zoning is and give you some general guidelines, etc.
From there, you can go on-line and there is detailed information for what allowable based on zoning. Beyond that, have to take a trip in person to Santa Rosa and dig into what septic, well and permit history shows for the property.
Hope this helps -