Most listings are in the $20's per square foot per year. The Petaluma region is going through a decrease 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 submarket has less expensive rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 33 listings have been made available, which means spaces 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 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 buildings in this area are approximately 2 floors. Most buildings in this area were built in 1996 and are Class A.