You will deduct applicable expenses for the half you live in (half the interest, half the real estate tax) on Schedule A. Rental related expenses (depreciation on one-half the basis in the building, half the interest and half the tax, half the insurance, and repairs related to the rental side only) on Schedule E. If the rent received exceeds the expenses, you have additional taxable income. If expenses exceed income, you have a rental loss, which may or may not be deductible against your other income, depending on your adjusted gross income. I hope this helps.
Real estate expenses for a duplex with one rental unit (one I live in) to be listed on Schedule E (supplemental income and loss) will not exceed rental income of the one rental unit so they will not transfer from that schedule as tax deduction against income. Is there any other location on the 2003 income tax return where costs related to duplex insurance, mortgage interest, real estate taxes, repairs, etc. can be shown and then transfer over as as a deduction from total income besides on Schedule E.