Suppose that the government passes a usury law that prohibits lending at more than 5% interest, but normal market rates are much higher due to inflation.
You have a customer, a Ms. Olsen, who wants to borrow at 20% and can put up her $100,000 store as collateral. Rather than refusing her request you decide to create a five-year contract with the following terms:
You hold title to the store and receive the right to sell her the store for $X at the end of five years.
If you decide to sell she must buy. In return you give her $80,000 in cash (the amount she wants to borrow) and the right to buy the store from you for $X at the end of five years. How can this contract provide you with a 20% annual rate of return on the $80,000?