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All you'll need is a loan contract. You can type this up yourself if you'd like. In the contract simply include a couple key points.
-List the exact amount loaned.
-Create an interest rate to charge and list it.
-List a term for the loan both for when payments should be received and by when the total loan should be paid off.
-Be sure to list both the lender and the receiver's full names and have each individual sign under their typed name.
-Finally, be sure to include some sort of penalty for late payments.
These are just basic features you need to include to make sure this is considered a loan, not a gift, in the eyes of the court should you need to do anything in the future.
Here is an example assuming John Doe is lending Jane Doe $10,000.
I, John Doe, hereby agree to provide a loan of $10,000 to Jane Doe on November 24th, 2007 with an annual interest rate of 5%.
This loan will be repaid in 12 equal payments to occur monthly beginning on December 24th, 2007. Each payment must be in the amount of $875.00. A late payment fee of $10 will be accessed for each week late a payment becomes.
I, John Doe (Signature), agree to the terms of the preceding loan contract.
I, Jane Doe (Signature), agree to the terms of the preceding loan contract.
As you can see by the example it doesn't need to be overly formal. You simply need the basics in writing with the signature of both parties agreeing to the terms.
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