Most listings are in the $70's per square foot per year. The Larkspur region is going through a an increase in rates. In the last 3 months, the median rate went up $4 per sqft per year. That's a 6% rise in rent.
Compared to the rest of the Bay Area market, the Larkspur region has greater rates, and you'll have to negotiate above asking rent to be in this hot region.
In the last 90 days, 6 listings have been listed, which means office spaces might be going fast. You'll want to be prepared to make an offer immediately. About 17% of the office spaces in the Larkspur are subleases, so you might be able to snag a great spot on a short term. 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 2,000 sqft. Most properties in this market are around 2 stories. Most buildings in this market were built in 1981 and are Class B.