A licensed Appraiser who provides service in that area can provide you with an accurate appraised value of the properties. The need (intended use) would determine the type value conclusion. Also, an appraiser would provide an unbiased opinion since he/she would not have a direct or indirect vested interest in the outcome of any current or future transactions regarding the properties. Here is a link to find an appraiser in the area: http://www.orea.ca.gov/
When you go to the site - click on the tab (on the left) "Find an Appraiser" - enter the city and zip - click search - a list of active appraisers in good standing will come up.