If you are just going to be in Riverside County without a homeowner's association, then Riverside County Planning would be where to start http://www.tlma.co.riverside.ca.us/planning/content/zoning/o
You may also want to check out the Wine Country Plan site listed in the left hand column of our blog
If you would like a list of email address to city planners etc...I have a list I can send to you. We have assisted many buyers in the area over the last 20 years.
Please feel free to look at our profile etc... http://www.BigAvocado.com
Scott and Shelley Weier
Cal State Realty
C2 Financial Corp
Another issue, you may or may not have considered but if you're getting a residential loan to purchase the home, converting it to commercial use (B&B) could trigger the acceleration clause in your mortgage.