On average, listings lease in the $30's per square foot per year. The West Covina region is experiencing a decline in rates. In the last 3 months, the median rate fell $3 per sqft per year. That's a 8% decline in rent.
Compared to the rest of the Metropolitan Los Angeles market, the West Covina submarket has more expensive rates, and you'll need to make a great offer to be in this hot region.
In the last 90 days, 22 listings have been posted online, which means new listings most likley are leasing quickly. You'll want to be prepared to make an offer immediately. About 5% of the available leases in the West Covina are subleases, so you will probably have to consider a longer term lease. 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 1,790 sqft. Most buildings in this market are approximately 2 stories. Most buildings in this market were built in 1980 and are Class B.