I don't believe I would ever buy brand new. Just too much depreciation and the really big problems will emerge in the first 10 - 20k miles.
I just looked and found a 25' Class C with 12k miles asking $25K. Brand new 25 is upwards of $50k. Big price difference and the used RV is still rather pristine.
Water damage in the cabover and kitchenette seems to be the biggest destroyer of value, so a THOROUGH going over with a fine toothed comb should confirm the shell is leak free. With reliable miles and good inspection, you could be fairly confident the coach is not coming to you with major problems. If you are the worrying sort, keep $10k (of the $25k+ you saved) in liquid reserve for "incidentals".
Jose