Wish i knew. I am thinking about looking into a B van when i get rid of my current piece of junk. We love to camp/travel but could live just fine with less RV drama. I know B vans will have issues as well but i have to think that rot issues would be minimal. The number one problem affecting RV's is water damage,be it from rain,washing,water line leaks, etc. My current TC has NEVER been washed and i avoid rainy conditions like the plague,especially driving in the rain. When washing i wipe the grime,bugs,etc off with a wet cloth. I also store my jacks in the rear floorboard of my truck to keep em out of water and away from the crud. I could go on and on but i think you get my drift.
The problem with B vans is $$$$$ . They are really spendy , new or used.