Is a storekeeper at a company that produces music cassettes obliged to leave his job, even though it is his sole source of income and he has a family to support?

Selling music tapes is a forbidden act because they contain musical instruments and objectionable lyrics. They deter people from obeying Allah and aid the wicked in their transgression. We advise you to seek a permissible occupation, for Allah facilitates sustenance for whoever fears Him. However, if you are compelled to this work and find no alternative, there is no harm in remaining in it until the necessity ceases. The limit of necessity is what one fears will lead to perishment or an unbearable hardship. It is to be estimated according to its extent, and when it ceases, the prohibition returns.