Most listings are in the $20'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 $6 per sqft per year. That's a 23% rise in rent.
Compared to the rest of the Bay Area market, the Petaluma region has lower rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 44 listings have been made available, so you'll want to check back regularly for new listings. About 2% of the office spaces in the Petaluma are subleases, so you will probably have to focus your search on direct office leases. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
Even though the median size is 2,820 sqft, there are still 0 office spaces below 2,000 sqft. Most buildings in this area are approximately 1 floors. Most buildings in this area were built in 1992 and are Class A.