The typical asking rate per listing is in the $20's per square foot per year. The Riverside region is seeing a an increase in rates. In the last 3 months, the median rate went up $6 per sqft per year. That's a 23% rise in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Riverside region has smaller rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 41 listings have been listed, so you'll want to check back regularly for new listings. 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 2,000 sqft. Most buildings in this area are approximately 2 floors. Most buildings in this region were built in 1989 and are Class C.