The typical asking rate per listing is in the $20's per square foot per year. The Petaluma region is seeing a decline in rates. In the last 3 months, the median rate decreased $2 per sqft per year. That's a 5% decline in rent.
Compared to the rest of the Bay Area market, the Petaluma region has smaller rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 31 listings have been made available, which means new availabilities 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 2,330 sqft. Most properties in this market are close to 2 stories. Most buildings in this area were built in 1996 and are Class A.