On average, listings lease in the $10's per square foot per year. The Yucaipa region is going through a a boost in rates. In the last 3 months, the median rate went up $16 per sqft per year. That's a Inf% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Yucaipa region has smaller rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 13 listings have been listed, which means new listings are probably 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 930 sqft. Most buildings in this region were built in 2008 and are Class B.