The typical asking rate per listing is in the $20's per square foot per year. The Lake Forest region is going through a decline in rates. In the last 3 months, the median rate fell $2 per sqft per year. That's a 6% decline in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Lake Forest region has smaller rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 35 listings have been listed, which means office spaces 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 1,800 sqft. Most properties in this area are close to 2 floors. Most buildings in this area were built in 1999 and are Class B.