Most listings are in the $40's per square foot per year. The Sonoma submarket is experiencing a a rise in rates. In the last 3 months, the median rate went up $50 per sqft per year. That's a Inf% increase in rent.
Compared to the rest of the Bay Area market, the Sonoma submarket has more expensive rates, and you'll need to make a great offer to be in this hot region.
In the last 90 days, 17 listings have been made available, which means new availabilities are probably going fast. You'll want to be prepared to tour spaces as quick as possible. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 380 sqft. Most properties in this area are approximately 2 floors. Most buildings in this market were built in 1974 and are Class C.