Willy was a close associate of Luis Lopez until Luis' arrest years earlier however upon his release from prison, Luis decided to go straight and so he cut all ties with Valerio and the Northwood Dominican Drug Dealers. An interesting note is that Henrique Bardas calls him Willy Valero (evident by the subtitles in-game and by how he says it) forming an inconsistency on how his name is spelt on the police database.
Believed to be attempting to compete with North and East Holland dealing operations but does not shift a significant volume of product.
It's possible, that Willy Valerio was supposed to be a friend of Luis Lopez instead of Henrique Bardas and Armando Torres, but was cut from the game during development. It's strengthened by the fact, that neither Henrique nor Armando have been mentioned in LCPD Police Database.