The typical asking rate per listing is in the $40's per square foot per year. The Tiburon region is going through a decline in rates. In the last 3 months, the median rate fell $24 per sqft per year. That's a 33% decline in rent.
Compared to the rest of the Bay Area market, the Tiburon region has smaller rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 3 listings have been listed, which means office spaces most likley are leasing quickly. You'll want to be prepared to make an offer immediately. 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 1,120 sqft. Most properties in this region are around 0 floors. Most buildings in this region were built in 1980.