They are not cheap.
I have three, living so close to the coast.
All mine are Meaco, a brand I can recommend.
Before buying anything, any brand, you could read the Meaco site as it has some good background information.
Don't buy one just for the van.
Ensure the one you buy, if you do, is suitable for your house.
My recommendation would be a compressor version (not the desiccant type (although I have one of those too)).
The compressor versions, imho, are much more suited to homes, and it will work well in your van.
Not cheap, but your home will benefit from it, and it can dry your laundry much cheaper than a tumble dryer !