The typical asking rate per listing is in the $30's per square foot per year. The Tiburon region is going through a a rise in rates. In the last 3 months, the median rate rose $40 per sqft per year. That's a Inf% increase in rent.
Compared to the rest of the Bay Area market, the Tiburon region has lower rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 7 listings have been made available, which means leases most likley are going fast. You'll want to be prepared to make an offer immediately. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,040 sqft. Most properties in this region are approximately 0 stories. Most buildings in this area were built in 1983.