Throughout his career, Billy has held various influential positions that have allowed him to effect positive change. His tenure at UPS, Aspira of Illinois, LUCHA, and the Center for Community and Leadership Development equipped him with invaluable experience in community organizing and advocacy. However, his role as the Alderman of Chicago's 26th Ward for 16 years truly propelled him into the public eye.

As an Alderman, Ocasio tirelessly worked to improve the lives of his constituents and enhance their living conditions. His most significant achievements include the creation of over 1,100 units of affordable housing, transforming the once-vacant Division Street into a vibrant Puerto Rican community business corridor called “Paseo Boricua,” and erecting the world's largest monument to a flag, the iconic Paseo Boricua Flags, that are now historical landmarks. These accomplishments earned him the well-deserved nickname "Mr. Paseo Boricua" and solidified his reputation as a dedicated advocate for his community.

Billy played a pivotal role in establishing The National Museum of Puerto Rican Arts and Culture (NMPRAC) in 2012, elevating Puerto Rican art and culture to a prominent position in the City of Chicago and throughout the United States and Puerto Rico. In 2013, Ocasio became the President and CEO of NMPRAC.

Under Billy’s leadership, NMPRAC flourished and became the only Puerto Rican Museum outside the island. His vision and tireless efforts led to the restoration of the once dilapidated Humboldt Park Stable and Receptory into a thriving Museum, raising over $10 million in funding and expanding the staff from two to eight members. Through educational programming, special events, docent-led tours, art workshops, and creating the Engage Conference, bringing together over 100 Puerto Rican Culture and Arts organizations from the diaspora to connect, learn, and collaborate.

In 2026, NMPRAC will become one of only four Latine accredited museums in the country, a distinction bestowed by the accrediting body, the American Association of Museums. This would also make NMPRAC the only Puerto Rican museum accredited outside the archipelago.