The few I have seen are older, I honestly didn't know they were still made. They come in 2 halves, like a manufactured home but without axles and wheels. Unlike a manufactured home or doublewide, they are set up on a weight bearing perimeter stem wall. The floor trusses or joists meet in the center and you will see a row of piers down the center of the crawl.
Stick em together, tack on some exterior trim and a ridge vent, some ridge cap and you are good to go.
The ones I run into are from the 60's and usually holding up really well. I think they are probably built better than your average doublewide. Judging by the roof framing pictures, it looks good to me (I probably shouldn't post this until we hear from JP).