Long Chassis

I'm in the dreaming stages right now. I really want to make a trailer that will fit into the wake of my mini-van and sleep 4 people with a rear kitchen. I've settled on a design that's about 16' long and around 6' wide. The problem is that it seems to be impossible to find trailers this size that aren't, ridiculously expensive, or really heavy (seems to be a lot of dual axle versions).
So does anyone have an idea of where I could find a suitable donor frame (craigslist seems to be empty in denver) or how much it would cost to have the frame welded if I cut all the pieces myself (again, does anyone know someone in the Denver/Boulder area). Along with that, I'd imagine a foamie could be supported by a fairly minimalist frame, are there any building guides?
Thanks
So does anyone have an idea of where I could find a suitable donor frame (craigslist seems to be empty in denver) or how much it would cost to have the frame welded if I cut all the pieces myself (again, does anyone know someone in the Denver/Boulder area). Along with that, I'd imagine a foamie could be supported by a fairly minimalist frame, are there any building guides?
Thanks