Most food production is highly seasonal or dependent on other seasonally produced products, so storage is essential. And whilst one person can live comfortably on about just 100 m², they would need significant space to store all the food, feed, firewood, and everything else that is necessary for self-sustainability. And since both food and firewood production can also wildly vary from season to season, I think storage of at least 2 years’ worth of supply is necessary to get through a few years of bad harvests, or even one with complete failure.

• A barn for firewood and hay – at least 50 m².
• A tool shed of at least 12 m², with a workshop just as big nearby.
• Rainwater storage of at least 30m³, either as a big pond or (better) as a covered tank.
• A small garage for a small tractor, lawnmower, hoe, and similar small machinery, and their fuel(s).
• A rodent-proof, dark, cold cellar, circa 12 m²
• Large-capacity freezer.
• If electric self-sufficiency is intended (I won’t concentrate on that), then sufficient battery storage is needed.

So now we know how much land one would need, and what fixtures would need to be on said land for long-term survival. And it appears to be a lot – and it is.