Offices are economy buildings in Tropico 5. They hire high school-educated or college-educated workers, and their effectiveness is based upon the number of residential buildings in the Vicinity. They can be built in the modern era.
Offices are great additions to your island as they bring in tons of extra income, and pay for themselves after usually less than 2 years if well placed. I woould suggest placing them near High popluation areas. I usually set up a downtown area next to popluation center which also includes my entertainment buildings, Cathedrals and Welfare buildings ( Supermarkets, Hospitals). They are also great buildings to put High School educated workers in once you have filled most of your factories.
The globalist will assign missions to build these buildings with rewards. You may also be awarded free office buildings after completing certain task in the modern era especially those assigned by the EU.
I would not suggest adding the Qualified Professional upgrade as I have not seen a dramatic difference in the money taken in, and you really want to concentrate your college level workers in Energy and research Sectors in the modern era.