How do I figure this out in an excel spreadsheet?

Method 1:

1. I put $1250 per month into notes that make monthly principal and interest payments at 15%
2. Notes have a 36-month term
3. Every month, I invest another $1250, PLUS the previous months cashflow in similar notes (the amount invested grows slightly every month)
4. After 36 months, what is the monthly cash flow from principal and interest, AND what is the value of the outstanding notes (underlying assets)

Method 2:

1. I borrow $10,000 (assume 6%) and buy exact same notes in bigger quantity
2. I use the $1250 per month, PLUS the cash flow to pay down the $10,000 instead of buying notes
3. When the note is paid off, I reborrow it and buy another 10k in notes
4. This pay-down and reborrow cycle gets shorter every time due to the added cash flow from previous flips
5. At the end of 36 months, how does the cash flow and underlying asset value compare to method 1?