On average, listings lease in the $20's per square foot per year. The Sebastopol region is experiencing a a boost in rates. In the last 3 months, the median rate increased $0 per sqft per year. That's a 1% increase in rent.
Compared to the rest of the Bay Area market, the Sebastopol region has lower rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 4 listings have been made available, which means leases are probably leasing quickly. You'll want to be prepared to make an offer immediately. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 270 sqft. Most properties in this area are close to 2 stories. Most buildings in this region were built in 1991 and are Class B.