http://www.rversonline.org/ArtGasDiesel.html
go to this website and review the numbers. Then at the end send him an email and he will send you his spreadsheet, "Evaluation of Ownership Cost of New vs Used RV.
It shows that in the 1 year you will lose 18% depreciation, then 12% the 2nd year, 8% the 3rd, 7% the 4th and 6% or less the years after.
This is based on what he found comparing the depreciation rate of rvs from several sources.
As soon as you drive off the lot, after purchasing, and turn around and go back they will depreciate your new rv 18-20%, that's even if you go back the same day.