On average, listings lease in the $60's per square foot per year. The Mill Valley region is seeing a a boost in rates. In the last 3 months, the median rate increased $12 per sqft per year. That's a 21% increase in rent.
Compared to the rest of the Bay Area market, the Mill Valley region has higher rates, and you'll need to pay a premium to be in this hot region.
In the last 90 days, 11 listings have been listed, which means new availabilities are probably going fast. You'll want to be prepared to tour spaces as quick as possible. About 18% of the listings in the Mill Valley are subleases, so you might be able to find a shorter term or below market rent. 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 300 sqft. Most buildings in this region are approximately 2 stories. Most buildings in this area were built in 1964 and are Class B.