The typical asking rate per listing is in the $10's per square foot per year. The La Center region is experiencing a an increase in rates. In the last 3 months, the median rate increased $16 per sqft per year.
Compared to the rest of the Greater Portland market, the La Center submarket has smaller rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 2 listings have been made available, which means leases most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. 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 600 sqft. Most buildings in this area were built in 2003 and are Class B.