There's a lot of chatter on the Internet about how much land is required to feed one person. You will not be surprised to learn that the answer is "It depends." It's somewhere in the neighborhood of "a few acres."
On a related note, I wonder how large of a greenhouse you would need to feed a family of four. Could you optimize a greenhouse to the point where it would only take a few hundred square feet?
Greenhouses have a number of benefits. You have a longer growing season, and good control over pests and weeds. You can optimize your water use, and you can use the structure's height to grow vertically where that makes sense.
I suppose you would want to get a few dozen neighbors in on the plan, so each of you can specialize on one crop per year then share the bounty. Rotating the crops across neighbors will help your soil, and it would diversify against problems in any one greenhouse. Plus it's easier on the home grower if he only needs to concentrate on beans this year and corn next year.
Obviously growing your own food only makes sense in a region where water isn't scarce. So let's say these homes with attached greenhouses are in Canada and have their own wells or other water source. And also imagine the homes are built for optimum energy efficiency, perhaps producing more power than they consume. If you have low ongoing expenses for energy, food, and water, your biggest expense is health care. And you're in Canada so the government takes care of that.
And imagine you mulch and recycle, so you have minimal garbage removal costs.
And let's say it's a community where everyone works at home and has high speed Internet connections. When you need a car, which is rare, you rent one. When you need tools, you borrow them from the shared tool shed.
I already know that none of my readers would want to live in the commie world I just described. I'm just curious how inexpensive you could make modern life for a family of four if you planned everything just right.