I would highly suspect a 1/2 ton van wouldn't work as a plumbers tool chest, so howabout Flower Delivery... all occaisions, weddings, parties, funerals. I wouldn't mess with that~
What about electric heaters? I borrowed one from a camper in a tvl trailer while I spent a few snowy cold nights in my old conversion van. It did the trick, down to about 25 degrees outside. And, the big windows were only covered with canvas curtains. I need to go north again and I will need...