There are 3 reasons to do

[moneymaker]

There are 3 reasons to do it,ok maybe 4.

1.interest free loan
2.if you default it does not affect credit score and the repayment may not show on credit report hence may not affect debt/income ratio.
3.not sure about refi but on purchase loan may extend out to 30 years.
4.if the market goes down with house prices, pay back will be buying stock @ cheaper price.Obviously this will not be true over 30 years.