What is the ruling on working in an installment company that grants loans to customers, to be repaid over 15 months with a 50% interest rate, without the customer receiving any goods?

If the nature of the institution's dealings is such that the customer buys a commodity at an installment price, and then authorizes the institution to sell it without condition, this is permissible. However, if it engages in forbidden forms such as usurious loans, or the prohibited bay' al-inah (where one buys a commodity in installments, then sells it back to the institution for cash at a lower price), or obliging the institution to sell the commodity to the customer, then working there is not permissible; because it involves aiding in sin.