As I said in my post, even at 5.69% (lower than current rates) a $592.6k interest only loan at 5.69% will generate $33.7k in interest a year, which is more than enough to breach the standard deduction for MFJ, even when you add in the extra $3100 for both being over 65. Even with some principle paydown, at current rates that are close to 7%, they would likely still breach the standard deduction for several years.
Did I say it was a credit? All I said was that there could be some tax savings when purchasing with a mortgage, where interest is deductible, and that needed to be compared to purchasing with the asset based loan and then doing a cash-out refi, where none of the interest would be deductible.
AJ