"so he isn't out $24,000 a year with NOTHING to show for it?"

Your components are going to include Interest expense, debt service (not expense), amortization (expense) and depreciation (if any; is expense).

"This however, for me will be a one time thing that I will never get involved in again"

We don't need you to be grateful; but this is Not your first time, and we are glad to help you, again.

You were the person trying to pay yourself for your Sole Proprietorship activity through payroll. It was quite a discussion. If you don't think you are learning anything, you should stop asking. If you intend, as you previously indicated, to help your clients, then you need to be learning this, taking CE, studying regulations and changes, and follow up when someone tries to point you to the right resources.

"not sure if those are correct or not, but they fill in the space without errors)"

Asking peers users about the program's functionality when you already know what you need to report is different than not even knowing what to call something per the IRS regulations that apply. Sure, you can plug numbers in somewhere, but are you doing a disservice to your client? For instance, it isn't clear if you are treating the payments as installment plan.

And someone overlooked getting guidance on this "sale" because the ability to pay Rent, not debt service, would have made the monthly payments an Expense. That's why business buy/sells require good planning.

"Now on to the other yet unanswered question... How do I show the Interest Expense on the son's return? The father gets the Interest Income via the 1099-INT that the son gave him, that's easy. How does the son write off this expense?"

@linettereally stated this nicely: "We all face these things in our daily business. I am not willing to provide that advice and the pitfalls in this forum."

This is not the place for "teach me to do taxes." This is peer users that are already staying current with their continuing education and update requirements, trying to use common software, and struggling with the same software, and questions for how to interpret some tax regulation that isn't clear or hasn't even been finalized by Congress. Although we are glad to Point you in the right direction, you need to learn these things yourself, off this forum, by proper studying, classwork, mentoring.

So, go to www.irs.com and look up "who must file 1099-INT" as a place to start.