As far as a prepayment penalty, I would not expect (or accept) one unless there are strings attached with a reduced interest rate and then pretty minimal months to wait and payoff. As others have mentioned, find a reputable dealer and focus on the PDI.
Also if you have a trust and want the Rv named under the trust, that gets tricky sometimes with financing, so extra steps to take afterwards.
Re: rule of 78 mentioned previously, don’t believe you’d run into that on an RV loan as they are typically 10-15 years and should be simple interest loans.