Duke is a nationally known commercial real estate broker with a long and distinguished career representing major real estate owners and developers, including the Charles E. Smith Company, the Lenkin Companies, Mid-City Developers, The Antonelli Family Trust, and The Kinser Family Trust, among others. He has been recognized for his role in significant transactions, such as the $85 million sale of 999 E Street in 2016 to Douglas Jamal. Duke has also been instrumental in pre-leasing large office buildings and acted as a straw representative in assembling nine lots before managing the development of a 160,000-square-foot office building for the American Medical Association at 1101 Vermont Ave, NW. Notably, he is credited with the largest office transaction in Northern Virginia in 1999.

Duke has represented prominent companies like Alcoa, U.S. Steel, Ahold, and the Dutch owners of Giant Foods and Stop and Shop in various real estate transactions over the years.

A past president of the Washington Board of Realtors, Duke also served on the Board of the National Association of Realtors. During his presidency, he successfully sponsored legislation to prevent banks from redlining minority loan applications in D.C. He played varsity basketball at Jacksonville University and completed his education at George Washington University in marketing.