After graduating college, Mills worked as deputy treasurer for the City of Philadelphia. He eventually became an
investment banker. During that time, he got to know
Robert L. Johnson, the founder of
Black Entertainment Television (BET). Eventually, Johnson hired Mills to work at BET. He credited Johnson with teaching him how to operate a business, calling his time with Johnson the "Bob Johnson School of Entrepreneurship". During his earlier tenure with BET, he launched BET's mobile and digital operations, and relaunched the Centric Pay TV network as
BET Her. Mills became president of BET in December 2017, replacing
Debra L. Lee. He announced he was leaving in December 2025. ==Personal life==