Most listings are in the $30's per square foot per year. The Tustin submarket is seeing a a boost in rates. In the last 3 months, the median rate went up $2 per sqft per year. That's a 8% increase 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 undervalued region.
In the last 90 days, 28 listings have come on the market, which means new listings most likley are going fast. You'll want to be prepared to make an offer immediately. 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 2,280 sqft. Most buildings in this market are close to 2 stories. Most buildings in this area were built in 1981 and are Class B.