The total interest payments in the first year will be about $10,740. Your tax savings (20 percent of $10,740) is $2,148.
For those thinking about buying a house to turn around and make money, in this example you paid $8592 in intrest (minus your tax savings).

So after 1 year your total payments were $18228, and you've only knocked about $3K off the principal. So you still owe about $177K on the original $180K loan.

something to think about.