If you are talking about federal income tax deductions, the state doesn't matter. I'm assuming you are concerned with your state income tax deductions.
The only difference in North Carolina tax law and federal is the maximum deduction.
You may deduct mortgage interest for your main home and a second home. A camper qualifies as a second home as long as it has sleeping space, toilet, and cooking facilities.
If you do not rent out your camper, there is no requirement that you use the camper during the year. If you do rent it out, then you must use it 14 days or 10% of the time it is rented, which ever is longer.
The total of mortgage interest and property tax is limited to $20,000.
§ 105-153.5
The amount allowed as a deduction for interest paid or accrued during the taxable year under section 163(h) of the Code with respect to any qualified residence plus the amount claimed by the taxpayer as a deduction for property taxes paid or accrued on real estate under section 164 of the Code for that taxable year. The amount allowed under this sub-subdivision may not exceed twenty thousand dollars ($20,000).
Tom