Most listings are in the $20's per square foot per year. The Vacaville submarket is experiencing a a boost in rates. In the last 3 months, the median rate rose $25 per sqft per year.
Compared to the rest of the Bay Area market, the Vacaville submarket has less expensive rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 1 listings have been made available, which means leases 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 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 470 sqft. Most buildings in this area are approximately 1 stories. Most buildings in this area were built in 1988 and are Class A.