On average, listings lease in the $70's per square foot per year. The Larkspur submarket is going through a a boost in rates. In the last 3 months, the median rate rose $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 higher rates, and you'll have to negotiate above asking rent to be in this hot region.
In the last 90 days, 9 listings have been listed, which means office spaces might be going fast. 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 1,480 sqft. Most buildings in this area are approximately 2 stories. Most buildings in this market were built in 1980 and are Class A.