The typical asking rate per listing is in the $10's per square foot per year. The Mendocino region is going through a a boost in rates. In the last 3 months, the median rate increased $19 per sqft per year.
In the last 90 days, 3 listings have been made available, which means listings are probably leasing quickly. You'll want to be prepared to make an offer immediately. 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 1,550 sqft. Most buildings in this region are around 1 floors. Most buildings in this region were built in 1988.