Most listings are in the $20's per square foot per year. The Riverside region is seeing a a rise in rates. In the last 3 months, the median rate increased $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 depreciated submarket.
In the last 90 days, 88 listings have come on the market, so you'll want to check back regularly for new listings. About 1% of the listings 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 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 2,140 sqft. Most properties in this region are around 2 floors. Most buildings in this market were built in 1989 and are Class C.