On average, listings lease in the $10's per square foot per year. The Rexburg submarket is experiencing a decline in rates. In the last 3 months, the median rate fell $1 per sqft per year. That's a 8% decrease in rent.
In the last 90 days, 5 listings have been made available, which means office spaces most likley are going fast. You'll want to be prepared to make an offer immediately. About 20% of the available space in the Rexburg are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
Even though the median size is 5,000 sqft, there are still 0 office spaces below 2,000 sqft. Most buildings in this area are close to 2 stories. Most buildings in this region were built in 2006 and are Class A.