On average, listings lease in the $20's per square foot per year. The Glendora region is going through a a boost in rates. In the last 3 months, the median rate rose $24 per sqft per year.
Compared to the rest of the Metropolitan Los Angeles market, the Glendora submarket has lower rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 7 listings have been listed, 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 sign a shorter term by taking over a previous 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 1,500 sqft. Most properties in this area are close to 2 stories. Most buildings in this region were built in 1985 and are Class B.
Not much of the real estate is used for commercial space, so it might be hard to find office space. Waste services is the dominant industry in this area. Most of the folk of Glendora work from home. Commuting between 30 and 45 minutes a day is the norm for those who opt to reside in this part of town.