On average, listings lease in the $50's per square foot per year. The Mill Valley submarket is experiencing a decline in rates. In the last 3 months, the median rate decreased $0 per sqft per year. That's a 1% decline in rent.
Compared to the rest of the Bay Area market, the Mill Valley region has greater rates, and you'll need to make a great offer to be in this hot submarket.
In the last 90 days, 11 listings have been made available, which means new availabilities 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 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 570 sqft. Most properties in this area are close to 2 stories. Most buildings in this area were built in 1964 and are Class A.