Most listings are in the $30's per square foot per year. The Sebastopol region is seeing a an increase in rates. In the last 3 months, the median rate increased $36 per sqft per year.
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 discounted region.
In the last 90 days, 22 listings have been made available, which means listings most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 27% of the listings in the Sebastopol are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,900 sqft. Most buildings in this area are close to 2 floors. Most buildings in this market were built in 1991 and are Class B.