Resale value for most RV's seems to drop like a rock. Unless its something with a cult following like Toyota Class C's or an Airstream you will be underwater on financing. I think the best bet is to buy used from a private seller, wave cash under their noses and play hardball with negotiations.
With reasonable care, an RV can last a long time. Our Toyota RV was 22 years old, but in great condition. It sold in 3 days for enough to buy our Jay Feather outright. I doubt we will be that lucky with selling the 25Z when the time comes, but at least we are not underwater on financing.
John & Nancy
Jay Feather 25Z 2007
Ford F-150 XLT 5.4 Triton 2008