If you paid contractors to make animal housing for you, you could conceivably spend more for the housing than you will for many of the farm animals. Conversely, when it's eventually time to sell, you don't want structures that reduce your property's value looking like the trash dump in Appalachia a hundred years ago. Therefore it makes practical sense to make structures which are reasonably appealing and attractive, especially if you value what your wife thinks ! Much of preparedness is assessing what you have available, and what could reasonably and safely be used for an alternate purpose. Here is just one of those ideas. The property owner was able to get someone to leave a giant wooden spool at his home. Such spools are used by power companies and even sometimes by contractors who are burying cable for other purposes. The owner was undaunted, and developed a plan to use the spool for something they needed.
The homeowner placed wooden slats all the way around the spool leaving an opening as a door. They already had the wood, although it needed to be cut to size. He secured them with screws so they could be repaired or easily altered later.
This is a clearer view.
This type of housing would not only be useful for a pig, but for goats, sheep, or even dogs. Although it's rather large, it could also be used for poultry. You could stain the outside of it or paint with protectant in order to increase its lifespan. You could also roof the top if you had roofing material available.
As long as the item you substitute for does the job and does not look ghastly, then inventive use of the items you have can be very beneficial.