I say build them if you are dead set on "DIY" with some scrounging you should be able to aquire the implement axle stubs cheaper than these choices:
https://www.google.com/search?q=imp...id-samsung-ss&sourceid=chrome-mobile&ie=UTF-8 [they have really gone up lately!]
The cube rental places used to be attached to towing companies in the past [around here anyway], but the business of rental cubes has exploded so now other moving options now exist. Like these things: [tilt free]
https://www.csrcoxons.com/
pay the price and follow the instructions and be onto building your "shop" I have moved garages when I was young and poor, not easy, and no longer as cheap as it was [literally and/or adjusted for time (inflation)]. So as a thing to consider, moving the 10' telephone poles required for "DIY" isn't light work either, to turn, you just rotate the logs as you wish to turn (pry bar and sledge work at the 12-16,000# load you are dreaming about. Like mentioned the ~9000 empty weight listed above is outside 2 high- lift/jack-all's to even lift one end for wheel/roller placement. Hire it out or adjust your longr term plans accordingly. This is just my experience, 3-4 garages, [#1 I was 10- 12 years old and just did as I was told/yelled at to do] countless metal sheds, and many dead vehicles/trailers. In short weigh out the price, timing, and the possibilities of injuries to yourself and more importantly your helpers and those financial risks. Again hire that out lots of specialized equipment and some matching skils, and they will be done in less than 2 hours if set up specifically for cubes/seacans. Harry