The typical asking rate per listing is in the $40's per square foot per year. The Napa submarket is going through a decline in rates. In the last 3 months, the median rate fell $4 per sqft per year. That's a 8% decrease in rent.
Compared to the rest of the Bay Area market, the Napa region has greater rates, and you'll need to make a great offer to be in this hot submarket.
In the last 90 days, 23 listings have been posted online, which means office spaces most likley are going fast. You'll want to be prepared to make an offer immediately. About 43% of the available leases in the Napa are subleases, so you might be able to snag a great spot on a short term. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
Even though the median size is 2,990 sqft, there are still 0 office spaces below 2,000 sqft. Most properties in this region are approximately 2 floors. Most buildings in this market were built in 1980 and are Class B.