Early work vans were designed to house manual laborers when on the job.  Great for highway and railroad crews.  These caravans were noted for poor ventilation and their spartan interior.  Three to six workmen were often housed in these wagons.

All the necessities for living with none of the comforts of home.  Cheaper than regular housing and mobile too.  One can see how this evolved into the later caravan.  These were expensive and not as well thought-out as later ‘vans.