BiggerPockets

Payment on $80K at 10% for 30 years is $702.06. You can calculate that with a financial calculator or in Excel. In Excel, the formula is: -PMT(10%/12,30*12,80000)

After five years, the balance on the loan will be $77,259.46. You calculate that with the FV function:
=-FV(10%/12,5*12,-702.06,80000)

Not quite sure what your intention is after the $30K payment. Typically a balloon payment would mean the entire loan must be paid at that time. So a "five year balloon" would mean the loan is to be paid off after five years.

So, maybe you mean the payments continue at the same $702.06 payment after the $30K payment. If so, the question is how many payments remain. You would calculate that with the NPER (number of periods) function:
=NPER(10%/12,-702.06,47259.46)

The answer is 99 payments plus a partial payment would still need to be make.

If instead you meant you want the loan to only have $30K remaining balance after five years, then you need to use a shorter amortization than 30 years. In that case you would calculate the payment using the PMT function and a future value of $30K after five years. That payment is $1,312.35, which equates to a 85.5 month amortization period.

So, then its easy. Its just the $702.06 payment. The balloon payment doesn't change the monthly payment. The payment is determined only by the rate, loan amount and the amortization period. The balance after five years is $77,259.46.

Angela,

The appeal of this particular note would depend on the payor's credit score and his/her actual potential to come up with that balloon payment.

No. If the payor refis, the investor still gets his/her balloon.