Pulsar obviously has it right as it's the quote out of the IRS Pub. I have used the second home deduction for many years for deducting camper or boat interest.
Please note that it simply states "sleeping, cooking, and toilet facilities". You only need some form of permanent sleeping facility, a permanent built-in toilet (or a head in the case of a boat), and something to cook with. My SeaRay had a single alcohol burner (built in) to satisfy the 'cooking' requirement, a small head, and a v-berth for sleeping but that's all it took.
My point is that you do not need a full blown kitchen with stove and oven, huge bathroom or a king sized bed in your RV to make the interest on it 'second home deductible'. Many/most/all folks with smaller campers, including some pop-ups, will qualify.
Tim
