During his career, he was managed by Mike Jones, who was also famous for managing
Gerry Cooney and
Wilford Scypion. Costello fought a lot of his early professional bouts around the
Hudson Valley-
NYC area, after a successful amateur career that culminated in a
Golden Gloves award. The
Kew Gardens section of Queens, New York eventually became his home, at least while he was champion. But before winning a title, he put together an early undefeated streak, which included a 10-round decision over Willie Rodriguez on
CBS television in November 1982. He and his management then became closely associated with the
CBS network, which aired several of his fights. The one and only title he held in his career, the
WBC junior welterweight title, was won by knocking out
Bruce Curry in the 10th round in January 1984 in front of a pro-Curry crowd in
Beaumont, Texas. He would then make three defenses of the belt, all in Kingston, and all by 12-round unanimous decision. His first foe as champion was
Ronnie Shields, with whom he traded first-round knockdowns before eventually securing the points win. Next was former WBC 140-lb. champion and veteran
Saoul Mamby, who replaced
Leroy Haley, another former possessor of Costello's belt, on five days notice. Costello defeated ex-champion Mamby by unanimous decision. His next fight was finally against
Leroy Haley. The result was a unanimous win over 12 rounds for Costello. Next, a
Denver, Colorado fighter named
Lonnie 'Lightning' Smith defeated him, knocking down and cutting the defending champion en route to an eighth-round stoppage in
New York City to claim the title in August 1985. Smith recovered from a first-round knockdown himself and dropped Costello five times before the fight was over. Billy kept coming back, next fighting three-time champion
Alexis Argüello in February 1986. Arguello, behind on points, stopped Costello in Round 4 after knocking him down. Costello then took some time off from the ring, fighting on a sporadic 'here-and-there' basis until the early 1990s. In his last bout in 1999, he defeated former world champion
Juan Laporte by ten round decision in a
Pay Per View fight, avenging a 1986 loss to LaPorte by his brother Vinnie. All in all, Costello's professional career had lasted an astounding 20 years, from 1979 to 1999, and ended with a win over a former world champion. His respectable career had only two losses, both to world champions. Costello is perhaps best remembered for his stoppage loss to
Alexis Arguello. ==Professional boxing record==