Hey Bernee,
I've had this very thing come up in my own experience. IMO, the key was that the Sub2 seller who wanted to buy another home decided to use an investor friendly, local lender with "in house" underwriting.
On the phone with the Sub2 seller's loan officer, I confirmed what the seller had told him which was that I had been making the monthly payments on the underlying loan for over a year. The loan officer asked for evidence, I gave it to him, the loan underwriters were able to adjust my Sub2 seller's Debt-To-Income (DTI) ratio based on that evidence, and he was ultimately able to get the loan for his new home!
If you have any questions, feel free to give me a call at 817-300-1132.
Thanks,
Robin CarrigerPresident
DFW REI Club
(817) 300-1132
Robin@DFWREIClub.com