Most listings are in the $20's per square foot per year. The Barstow submarket is experiencing a a rise in rates. In the last 3 months, the median rate rose $24 per sqft per year. That's a Inf% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Barstow submarket has lower rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 5 listings have been made available, which means new availabilities most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. 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 1,600 sqft. Most properties in this area are approximately 2 stories. Most buildings in this area were built in 1970 and are Class B.