Good news, you don't need one. If it is not considered a mortgage loan you they will not issue one to you.
Your interest may qualify as mortgage interest. Continue reading for more information.
You are allowed to deduct mortgage interest on your first and second home. A home for IRS purposes is described as follows:
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.
If your RV has the requirements then you can fully deduct the interest on a loan secured by your RV if the total amount of the loan is below $750,000.
You will have to prorate the amount of deductible mortgage interest that represents the RV if there are loan proceeds used for other purposes besides the RV.