Most listings are in the $50's per square foot per year. The Mill Valley submarket is seeing a decline in rates. In the last 3 months, the median rate fell $17 per sqft per year. That's a 23% decrease in rent.
Compared to the rest of the Bay Area market, the Mill Valley region has greater rates, and you'll need to pay a premium to be in this hot region.
In the last 90 days, 6 listings have come on the market, which means spaces most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. 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 250 sqft. Most buildings in this region are approximately 2 floors. Most buildings in this area were built in 1964 and are Class A.