Compared to prefabricated paint booths, twenty-foot shipping containers are extremely cheap and plentiful. You can hardly buy the materials to build a booth for what they cost. And yes, they can be delivered and set inside an existing building...or left to stand alone if you have a safe way to keep it heated during use.
I'm in a rural area and I use an axial fan (grain bin dryer fan) to extract the dust through a plenum near the ceiling, and then down through a cabinet and then through the floor at the far end. It's hard-wired for lights and it's plumbed for air. I custom built the 7-foot swing arm lamp.
We use ours for sandblasting cemetery monuments and boulders, but I've done plenty of painting projects in it as well. I paid a little extra and bought a nicer looking "one-tripper" (they're essentially brand new, and used just once).
If I had it to do again, I would have gotten a high-cube (9'6" high, instead of 8'6").
JB