The typical asking rate per listing is in the $20's per square foot per year. The Petaluma submarket is seeing a decrease in rates. In the last 3 months, the median rate decreased $4 per sqft per year. That's a 14% decline in rent.
Compared to the rest of the Bay Area market, the Petaluma region has less expensive rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 45 listings have been posted online, so you'll want to check back regularly for new listings. About 2% of the listings in the Petaluma are subleases, so you will probably need to sign a longer term lease with the landlord directly. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,470 sqft. Most buildings in this market are around 1 floors. Most buildings in this area were built in 1990 and are Class A.