The CalHFA Approved Lender must complete this form and provide it to the borrower. Start the body of your letter with a brief summary of why you're writing it and the amount of money you'd like to borrow.An IOU (I Owe You) is a legal document that sets out the details of a loan made between two people, a borrower, and a lender. When someone offers to help you make a down payment on a house, your lender will require a gift letter for a mortgage. Here's what it includes. Provide a clear explanation: Your letter should acknowledge and indicate why something happened. LendingTree does not include all lenders, savings products, or loan options available in the marketplace. How Does LendingTree Get Paid? If you prefer to email us, fill out the form below and an associate will contact you to review the loan scenario and provide a quote. First Name(Required).