Final answer:
When a seller takes back a purchase money mortgage from a buyer, the terms and conditions of the mortgage must be set forth in writing. This means that there needs to be a written agreement between the seller and the buyer that clearly outlines the terms of the mortgage.
Step-by-step explanation:
When a seller takes back a purchase money mortgage from a buyer, the terms and conditions of the mortgage must be set forth in writing. This means that there needs to be a written agreement between the seller and the buyer that clearly outlines the terms of the mortgage, such as the interest rate, repayment schedule, and any other applicable conditions. It is important to have these terms in writing to ensure that both parties are aware of their rights and responsibilities. Therefore, option C is the correct answer.