Most listings are in the $20's per square foot per year. The Corona submarket is going through a decrease in rates. In the last 3 months, the median rate fell $3 per sqft per year. That's a 12% decline in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Corona region has lower rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 84 listings have been listed, so you'll want to check back regularly for new listings. About 1% of the listings in the Corona are subleases, so you will probably need to consider the implications of signing a direct lease with the building. 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 1,500 sqft. Most buildings in this area are approximately 2 floors. Most buildings in this area were built in 2005 and are Class A.