On average, listings lease in the $20's per square foot per year. The Glendora region is experiencing a a rise in rates. In the last 3 months, the median rate went up $24 per sqft per year.
Compared to the rest of the Metropolitan Los Angeles market, the Glendora region has lower rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 7 listings have been posted online, which means spaces most likley are going fast. You'll want to be prepared to make an offer immediately. About 157% of the available space in the Glendora are subleases, so you might be able to snag a great spot on a short term. There aren't many listings below 2,000 square feet available, 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 market are approximately 2 floors. Most buildings in this area were built in 1985 and are Class B.