The typical asking rate per listing is in the $30's per square foot per year. The Corona submarket is going through a decline in rates. In the last 3 months, the median rate decreased $0 per sqft per year. That's a 1% decrease in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Corona region has smaller rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 16 listings have been listed, which means spaces most likley are leasing quickly. You'll want to be prepared to make an offer immediately. About 194% of the office spaces in the Corona are subleases, so you might be able to sign a shorter term by taking over a previous lease. 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 1,800 sqft. Most properties in this market are around 2 stories. Most buildings in this area were built in 2005 and are Class B.