Newbie question regarding rental income

[Josh Corby]

Do you deduct the amount of mortgage principle you paid from your rental income? For example, if you make $15,000 GROSS rental income, but you paid $5,000 of the mortgage principle for the year, is your net income $15,000 or $10,000. I know you can deduct other expenses such as mortgage interest, repairs, and operating expenses. Would the mortgage principle be considered an operating expense and therefore deducted as such? Thank you.