On average, listings lease in the $30's per square foot per year. The Diamond Bar submarket is going through a decline in rates. In the last 3 months, the median rate fell $1 per sqft per year. That's a 2% decrease in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Diamond Bar region has greater rates, and you'll need to make a great offer to be in this hot submarket.
In the last 90 days, 19 listings have been posted online, which means leases are probably going fast. You'll want to be prepared to tour spaces as quick as possible. About 5% of the listings in the Diamond Bar are subleases, so you will probably need to sign a longer term lease with the landlord directly. 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 1,530 sqft. Most properties in this region are around 2 floors. Most buildings in this market were built in 1987 and are Class B.