Most listings are in the $10's per square foot per year. The Pharr region is experiencing a an increase in rates. In the last 3 months, the median rate rose $16 per sqft per year.
In the last 90 days, 1 listings have been posted online, which means new listings most likley are going fast. You'll want to be prepared to make an offer immediately. About 500% of the available leases in the Pharr 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.
The standard measurement for office space in this area is around 1,250 sqft. Most properties in this market are approximately 3 floors. Most buildings in this area were built in 2012 and are Class B.