On average, listings lease in the $20's per square foot per year. The Covina region is experiencing a decline in rates. In the last 3 months, the median rate decreased $13 per sqft per year. That's a 35% decrease in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Covina region has smaller rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 10 listings have been listed, which means new availabilities most likley are going fast. You'll want to be prepared to make an offer immediately. 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 2,270 sqft. Most buildings in this region are around 2 stories. Most buildings in this area were built in 1981 and are Class B.