When Alfredo became sick, the much younger Manny wanted to go to work to earn money for his family. However, Alfredo forbade it because he wanted Manny to concentrate on his studies.
However, Manny offered to replace Alfredo as Lisa Cuddy's handyman. When Cuddy refused because that's not what Alfredo wanted, Manny confronted her about not visiting him, not knowing that Stacy Warner had forbade her to see Alfredo for fear she would admit liability for his injuries.
However, Alfredo realized he would lose one of his jobs if Manny didn't fill in for him and explained to him in Spanish to replace him. House found out and confronted his mother in Spanish about where he had gone. He figured out Manny couldn't be at a legitimate job as no-one would accept a thirteen year old, and figured out it must be somewhere illegitimate, most likely a cockfight.