Bought and sold more than 28 Pups over the past 30 years. Other than the hardside models ( and even this with canvas over the beds), they all have that tent trailer aroma. It is not mold. It is the canvas. Ever unpack a canvas tent after storing it? Same thing. Odor goes away after airing out.
As far as stains, not too easy to remove from canvas, Sunbrella or any other canvas alternative materials.
My current tent trailer is a 1986 Palomino with the folding hard-side walls. This model had vinyl over the beds and this has been the best I have had. Very easy to clean.
In these 30 years, I have had them all including Starcraft, Coleman, Palomino, Venture, Wheel Camper (antique), Viking, Jayco, you name it and my favorite has been the Palomino whether canvas or hard side. Why? Palominos have a roof system that uses a one piece aluminum sheet on the roof and the same aluminum inside on the ceiling. This is far better than most other brands that use a vinyl covered hardboard for the ceiling. Many I have purchased had this type of material peeling or stained because the trailer was folded up wet or because of sweating or water damage. Palominos don't have this issue with the aluminum ceiling. Just all MHO.
Just be sure to inspect the roof for water damage and dry rot. common issue with tent trailer roofs that were not properly maintained.
WHATEVER YOU DO, DO NOT PURCHASE A COLEMAN PRODUCT WITH THE ABS "PLASTIC" ROOF. These were well known for defective manufacturing with the roofs delaminating, cracking and sagging. Also, if you come across one that has a roof-air and the roof sags in the middle, most likely the roof has water damage.