It has nothing to do with tax writeoffs or anything. In my current job the house will most likely be paid off within a year. I did it to establish credit in commercial loans. Showing that I can pay off such a large commercial loan in 1 year or less will then allow me to take a larger loan next time to buy a building. Getting a regular mortgage and paying it off in 1 year would not look too good on credit, the bank even told me they tend to frown upon people paying off 30 year loans in 1 year.