On average, listings lease in the $20's per square foot per year. The Riverside region is seeing a a boost in rates. In the last 3 months, the median rate rose $2 per sqft per year. That's a 6% rise in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Riverside region has less expensive rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 89 listings have been listed, so you'll want to check back regularly for new listings. About 1% of the available space in the Riverside are subleases, so you will probably have to focus your search on direct office leases. There aren't many listings below 2,000 square feet posted, 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 region are approximately 2 floors. Most buildings in this market were built in 1989 and are Class C.