On average, listings lease in the $40's per square foot per year. The Sonoma region is experiencing a a boost in rates. In the last 3 months, the median rate went up $41 per sqft per year. That's a Inf% rise 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 submarket.
In the last 90 days, 15 listings have been listed, which means new listings most likley are going fast. You'll want to be prepared to make an offer immediately. 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 830 sqft. Most properties in this market are close to 2 floors. Most buildings in this market were built in 1978 and are Class C.