To my mind, survivalism goes beyond prepping, so as to add complete or near-complete self-sufficiency. And that is beyond the preparedness level of most serious preppers. So while a prepper might have an extensive backyard garden, as a supplemental food source, the survivalist seeks to provide all (or almost all) the food needed to survive from their own resources. What would it take, at a minimum, to grow enough food for survival all on your own?
At a bare minimum, you would need a half acre per person. But taking account the possibility of crop failures, lower yields due to less intensive care of the crop (see #2 below), weather
problems, pests and plant diseases, and all manner of difficulties a small farm might endure — I would double that amount of land to one full acre per person.
The land has to be arable. In other words, the soil must be ready to plant, with minimum preparation (a quick tilling). Otherwise, it would take too much labor, equipment, and fertilizer to work the land. We are not talking about a commercial farm, that can put money in, if it gets money out. For survival purposes, you would need to minimize all inputs, or else you won’t be able to afford the crops.
And the land might need to be zoned for agriculture, as this type of backyard mini-farm is far beyond the scope of a backyard garden.
If you are not selling the crop, then you can’t afford to hire workers. Share cropping is sometimes an option. Workers get a share of the crop instead of pay. But that requires a much larger area of land.