If you want to finance your RV using a mortgage and use the tax deductions see this article:
Your RV is accepted as a home or second home by the IRS
For you to take a home mortgage interest deduction, your debt must be secured by a qualified home. This means your main home or your second home. A home includes a house, condominium, cooperative, mobile home, house trailer, boat, or similar property that has sleeping, cooking, and toilet facilities.