Most listings are in the $30's per square foot per year. The Riverside submarket is seeing a a rise in rates. In the last 3 months, the median rate went up $10 per sqft per year. That's a 40% rise in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Riverside submarket has lower rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 41 listings have been posted online, so you'll want to check back regularly for new listings. 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 2,000 sqft. Most buildings in this area are close to 2 floors. Most buildings in this region were built in 1989 and are Class C.