[howLongHowLong]

3 acres could definitely provide one with most enough to live on if one keeps animals, preserves surplus, and expands their definition of seasonal. "Four-Season Gardening" by Elliot Coleman, a great book on the subject, shows a green house strategy that involves no added energy (in Maine, no less). I imagine thoughtful addition of active control could improve output.

The hardest part is growing enough protein, which is why livestock is sort of a necessity for subsistence living unless you live someplace with accessible and abundant fish or game. One past solution was collectively owned and worked acreage devoted to beans, milk or similar, though I suppose it could be argued that leads us back here, eventually, once someone gets the idea to sell the surplus of that. (It did once, already)

TL;DR Check out "Four-season Gardening" by Elliot Coleman for interesting ideas on expanding your growing season without adding electricity