Generally speaking, there is nothing deductible about buying something. If you finance a home, you can deduct the mortgage interest. But if you buy it with cash, there is nothing tax deductible about that, including paying off part of the principle early (which is the same as buying part of the house with cash). It doesn't matter where the cash comes from, and the bonus is still taxable.
If you buy property that will be used in business, that is not deductible either, but you can depreciate it (which is similar in some ways to a deduction, but different in other ways) which is a subtraction from your business income, not your personal income.
Paying extra principle is ultimately to your benefit because is reduces the amount of interest you will pay in the long run. But it is not an immediate tax deduction.
