Most listings are in the $20's per square foot per year. The Vacaville region is seeing a an increase in rates. In the last 3 months, the median rate increased $27 per sqft per year.
Compared to the rest of the Bay Area market, the Vacaville submarket has smaller rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 1 listings have been posted online, which means new availabilities most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. About 100% of the available leases in the Vacaville 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.
The standard measurement for office space in this area is around 700 sqft. Most properties in this region are around 1 stories. Most buildings in this market were built in 1988 and are Class B.