For people who have land in front of their own house, it is very nice, because they can immediately turn their home page into a small garden to grow plants and fruits that can be consumed. But this will not be able to be run by those who only have a house without having a qualified front yard. So I think the advice you give is very limited because it is only for certain people.
I think if we consider some time and space saving options, you would need only a minimal amount of garden to survive on.
Something has lately sparked my interest. Namely indoor gardens aka greenhouses and potato growing bags. The growing bags are interesting because you would not have to actually uproot and harm/destroy the potato plants, rather you open a section of the bag and take out the grown potatoes. The plant itself stays unharmed and continues growing even more potatoes for the maximum yield, until exhaustion. Unlike if grown in a field, its more efficient, I would think.
It takes 3-4 months for the plant to grow to the point of harvest and with a potato bag, even though the next harvest will not be as plentiful, it should only take 10 weeks for new potatoes to fully grow.
Whether or not thats more efficient than replanting and waiting 3-4 months for a full harvest can be a point of argument...
You could grow in a greenhouse, or even in a room with sufficient sunlight. Even in winter, so the question is, seeing as you do not need to replant every time, how many perpetually growing potato plants do you need to harvest a steady amount of potatoes and survive?
edit: I am not plant expert, so I might be completely off on how many times you can harvest from a single potato plant. A strategically timed replanting could achieve the same result.