@ldbeng wrote:
How do I report the loan down payment and principal payments made in 2019 as a business expense on Schedule C?
The loan down payment and principals payments are not deductible business expenses that would be reported anywhere on Schedule C; only the interest on the loan is deductible.
However, you should track of the loan proceeds and liability outside of TurboTax. Essentially, that would be a bookkeeping entry.