Some people need a basic finance class. Why not borrow 5% (tax deductible) and keep your money in an investment earning 7%? Depreciation of the coach is totally irrelevant to this discussion.
Check with your accountant about 2nd home tax deduction. I thought I heard some things might be changing with that under the recent tax reform.
For the money being talked about, a $200 prepayment penalty is not even worth thinking about.
5% interest rate on the purchase isn't too bad these days. I've heard/read around here that credit unions will generally be the best. Home equity lines might also be good. Older coaches often times won't qualify for the best rate.