The Bible does not tell the occupations of all the disciples except for Thomas and Bartholomew, who were fishermen, and Judas, James and Phillip, who were sorts of tradesmen. Regardless of their work, they decided to quit and follow Jesus.
Some of their skills became relevant to the work they were commissioned to do. Matthew believed that God would provide for all their needs so having an occupation was not necessary. During the commissioning, they were not allowed to carry clothes, money, sandals, bags or other relevant items for their journey. Such items were to be provided by the people they visited.