Most BP sales these days go through the internet. There is a company called ship your reptiles that specializes in shipping reptiles. They take the hardest part of selling online out of the equation.
http://www.shipyourreptiles.com
Tubs hold humidity in very well, in most cases humidity is actually too high and holes need to be drilled in the tubs to let some out.
Tubs on the other had are harder to heat than glass tanks or professionally made reptile cages.
Here is a thread on setting up a tub:
http://ball-pythons.net/forums/showt...e-Basics-*DUW*
The air temperature inside a tub as well as the cool side of a tub is determined by the temperature of the room that the tub is in. This means that the room needs to be heat to 75+ F (80 F would be best) year round.