Most listings are in the $20's per square foot per year. The Tustin region is seeing a decline in rates. In the last 3 months, the median rate fell $5 per sqft per year. That's a 15% decline in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Tustin submarket has lower rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 27 listings have come on the market, which means spaces are probably leasing quickly. You'll want to be prepared to make an offer immediately. 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 1,130 sqft. Most properties in this market are around 2 floors. Most buildings in this market were built in 1980 and are Class B.