Marcellus, who immigrated from Haiti and became a United States citizen, began his career as a dishwasher at a hotel in North Jersey and, after moving to the Atlantic City area, worked his way up from security officer to supervisor in housekeeping and food and beverage, as well as shift manager in restaurant services. In 2014, he founded Marcellus Integrity Multi Services, a small business providing income tax preparation, accounting, and consulting services to residents and local businesses. Beyond his professional work, Marcellus is deeply involved in the community, serving as a board member at Mount Zion Baptist Church in Pleasantville, one of the area’s largest congregations. He holds a Bachelor's and Master's degree from Fairleigh Dickinson University and a doctorate from Walden University.