On average, listings lease in the $30's per square foot per year. The Petaluma submarket is going through a a rise in rates. In the last 3 months, the median rate increased $7 per sqft per year. That's a 30% rise 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 discounted submarket.
In the last 90 days, 34 listings have been posted online, which means office spaces are probably leasing quickly. You'll want to be prepared to make an offer immediately. About 3% of the listings in the Petaluma are subleases, so you will probably need to consider the implications of signing a direct lease with the building. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
Even though the median size is 2,840 sqft, there are still 0 leases below 2,000 sqft. Most properties in this market are close to 1 floors. Most buildings in this area were built in 1992 and are Class A.