Yes. The situation is analogous to borrowing money to invest in the stock market: Your profit is the profit you make from the stocks minus the interest you pay on the loan, and that difference is what you pay tax on.
In Canada, a mortgage on a principle residence is not tax deductible, since Canadian tax law doesn't consider where you live to be an "investment"; this is balanced by a principle residence being exempt from capital gains tax.
If you have a business that borrows to buy and then rent houses, the same principle pertains; the interest on the mortgage is an expense.
Only in proportion to the fraction of the house which constitutes your home office.
If you have a business that borrows to buy and then rent houses, the same principle pertains; the interest on the mortgage is an expense.
Right -- mortgage interest is a business expense when it's paid for a business reason. A principle residence is not considered to be an investment; it's considered to be a home.
Seems to be another one of those perks that got removed just as I reached the point in life where I'd benefit from it.