Irregardless of any type of "4 seasons" or other package you're able to find, there will be other winter time preparations so that you can live comfortably and have the plumbing work. You'll have some sort of auxiliary heat and a dehumidifier. You will also have skirting and if you plan to travel in the Winter, you should consider how you'll make the skirting easy to assemble and disassemble.
Full-timing in the Midwest isn't for sissies but if you prepare correctly, it can and is done.
BTW, get the most complete 4 seasons package that you can. That package would include dual pane windows and an insulated underbelly.