unless you're charging interest you're running afoul of IRC section 7872 since the loan is more than $10,000.
it would require you to impute interest income, taxable to you, and then since you aren't collecting it treat it as a gift to the borrower.
and if you're charging interest the IRS would say part of each payment made to you is interest and part principal
doesn't matter that you'll be collecting the interest as the final payment.
