Most listings are in the $20's per square foot per year. The Petaluma submarket 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 smaller rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 31 listings have been listed, which means office spaces most likley are leasing quickly. You'll want to be prepared to make an offer immediately. 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 2,330 sqft. Most buildings in this region are close to 2 stories. Most buildings in this area were built in 1996 and are Class A.