You will spend quite a bit on the proprietary resin bags. The TDs in Wisconsin isn't as conducive to DI only systems unless you use it very sparingly. They say 300 gallons from a single bag unit. I still haven't' seen anything about the TDS level they base that off. I imagine it's 200 TDS or less. As for space this will take up about as much floor space as a half cube DI tank.
It will vary Conner since it depends on the operators skill level the condition of the glass type of windows, number of windows (square footage isn't usually a good indicator of window count in my area), and whether it's hydrophobic (water beads and takes longer to rinse it for good results) or hydrophilic (water sheets so you can rinse quickly).
You will get about half a gallon a minute out of the unit (give or take) so if you had a house with 40 casement windows in fair condition that were hydrophilic and you were an average user of the wfp it could take under an hour not including setup or breakdown time.
Change any of those conditions and the time varies a little but unless the windows are horribly hydrophobic or extremely dirty I don't think longer than 1 hour and 15 minutes.
Don't forget to check the TDS of your area (it will vary from neighborhood to neighborhood so be aware of that) and get a firm answer as to what the TDS is that Unger says gets you 300 gallons out of the small unit.
Then you can get a rough estimate of run time based on 1/2 gallons a minute. If you get 300 gallons out of it in your area then that's 150 minutes of run time.
My little money maker. Refills are about 54, lets say 65 with shipping. I can expect to get 250 gallons out of it with my tds. I run about a gallon a min. Average house takes about an hour. So about 16$ in resin per job. To lower that you can reuse the bags with your own resin. Looks very easy to refill. just ziptied shut.