I'm not in the mortgage business so, anyone, please correct me if I'm
wrong.
It seems to me that if you purchase a mortgage at a discount, the
monthly payments that you will receive will be based on the original
terms set out, unless new terms have been negotiated and agreed to.
Therefore, if Jim purchases a mortgage at a discount and receives
monthly payments based on the original terms of the mortgage, the
calculation to determine his yield would be as follows, provided
interest is compounded monthly, not in advance:
Original Mortgage
---------------------
Principal: $100,000
Amortization: 25 Years (300 months)*
Interest Rate: 8%
Monthly Payment: $771.82 [=PMT(8%/12,25*12,100000)]
*Assuming mortgage amortized for 25 years
Interest Yield on Discounted Mortgage
---------------------------------------------
Principal (Discounted): $95,000.00
Amortization: 280 months
Monthly Payment: $771.82*
Interest Yield: 8.35% [=RATE(280,771.82,-95000)*12]
*Mortgagor continues to make the same monthly payment