Iran's banking system is partly based on the mudarabah concept from Islamic economics. The banks operating under this system act more like business partners than lenders. The banks earn a share of the profits from the borrower rather than collecting interest payments. Versions of this approach can also be found in other economic systems. For example, some European banks and their borrowers invest in each other to form closer business relationships.

Consumer loans can be arranged in a similar fashion if the lender collects a share of future income instead of interest payments. For example, some people are eligible to arrange for income-based repayment of federal student loans. If the borrower has relatively low income after they graduate, their initial loan payments are reduced, and their monthly payments increase over time as their income grows. The repayment term may be extended under this system, and some of the debt may be forgiven if the borrower's income remains relatively low over time.

Suppose banks extend this income-based repayment approach to consumer credit like car loans. Do you think people would consider borrowing money for a car under an income-based loan? Would people be willing to pay a higher interest rate in exchange for more flexible repayment terms on a car loan?