Djprinter is right, except it won't take me that long to model my shack (something I will be doing but I need to model a couple greenhouse contracts first.) It all really depends on the skill of the modeller and their knowledge in residential construction. Scanning would help with the exterior, I guess, but if you want to print it to have rooms and the like, you'd be better off creating a couple of boolean boxes within the scan to create rooms, at which point you'd have to add support structures when printing the floors and other such surfaces. Most printing software automatically adds the removable supports, so you'd save some time on that too.

I guess my biggest question would be is why? What function will this project have? How detailed will it have to be? The answer could help you manage your time better.