Most listings are in the $20's per square foot per year. The Apple Valley region is going through a an increase in rates. In the last 3 months, the median rate went up $5 per sqft per year. That's a 30% rise in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Apple Valley submarket has lower rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 3 listings have been listed, which means leases might be going fast. 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 2,100 sqft. Most properties in this area are around 2 stories. Most buildings in this region were built in 1989 and are Class B.