Age: 34 years, 8 months
Place of Birth: Tralee
Height: 180 cm
Tralee native Billy played youths football with Tralee Dynamos and Kingdom Boys before joining Shelbourne's youth set up. In January 2005 he was signed by Sunderland manager Mick McCarthy.
In November 2007 he went on loan to Accrington Stanley where he made 7 league appearances. He was released by Sunderland in June 2008.
In August 2008 Billy returned to Ireland and signed for Derry City. His Candystripes debut came as a substitute in a 2-0 Setanta Cup win over Glentoran at the Brandywell on 2 September '08 and he made 4 league appearances before the end of the season. In January 2009 he moved south to sign for Cork City, scoring on his debut, away to Sligo Rovers on 7 March. He scored seven times in the league as City finished third under Paul Doolin, but the close season proved disastrous for the club who were wound up amid huge controversy shortly before the 2010 season began.
Billy moved on in January 2010 when he signed for Shamrock Rovers where he made 34 league appearances and scored six league goals as Rovers won the League title. He also played in the 2010 FAI Cup final which the Hoops lost on penalties to Sligo Rovers. In 2011 Billy played in 35 of Rovers thirty-six league games, scoring nine goals, as Rovers won their second consecutive league title. Billy also scored against PAOK in the Europa League when Rovers became the first Irish side to qualify for the Group stage of a major European competition. In 2012 season Billy made another 29 league appearances, scoring three times, as Rovers finished fourth in the league. Billy remained a part of Shamrock Rovers' squad for the 2013 season under new manager Trevor Croly but failed to score in 26 league appearances, though he did win the EA Sports Cup and Setanta Cup.
Billy was released by Shamrock Rovers in October 2013 and returned to Cork City where he joined up under new manager John Caulfield. He topped the club's scoring charts in 2014 with thirteen league goals and another four in the Cups as City finished runners up to league champions Dundalk. In 2015 Billy continued his scoring run, netting ten times in 25 league appearances as Cork finished runners-up to Dundalk once more. He was also a part of the team that played in the FAI Cup Final which City lost 1-0 to Dundalk after extratime. In November 2015, Billy left Cork City and, later in December, he and his brother Darren signed for St. Patrick's Athletic.
Billy made his league bow for St Pats on the opening night of the 2016 season against Galway United at Richmond Park and scored four times in 27 league outings. He also picked up an EA Cup winner's medal when the Saints beat Limerick 4-1 in the final.
In January 2018, Billy signed for Limerick FC ahead of the new season.