Wow, you're concepts of the sustainability of local food sources is... I can't think of a polite way to say that you're nuts.
Modern cities, of which I have lived recently in both rural and urban, do not have the capacity to support their own populations, nor do the populations have the knowledge or experience to sustain themselves on their own as say, 150 years ago. The average population doesn't know how to clean a fish, butcher a pig/cow/chicken, or how to grow and when to harvest plants.
Lets pretend for a moment that there is a sufficient education campaign to teach people how to grow crops. Cities do not have the horizontal surface area capacity to handle sufficient crop growth.
Importing of food stuffs costs fuel, which would be heavily taxed. Harvesting foodstuffs require fuel, which would be heavily taxed. Refrigeration costs electricity, which would be heavily taxed.
I'm sure we could go back to horse drawn wagons using ice to transport much smaller quantities of food stuffs at a time, but that is impractical.
I can only presume you know little of running a business, as regulatory, embedded taxes and other "costs of doing business" and only be absorbed so much before they are passed onto the consumer or the business goes broke. This raises the final cost at retail out of the range of lower income households. Another "cost of doing business" from increased regulatory and embedded taxes is the need to eliminate positions of employees to keep a business afloat. This means another person who is now low income that can't afford the cost of foodstuffs or other products that have risen in price.
Congratulations on your ability to live close to your job. You are fortunate in that regard. However, there are millions of people that must commute long distances, such as all the people that can't afford to live in new york and must travel from jersey. Don't bother going into some "well if gov taxed 1% or forced lower housing costs so they could live in the city they work in blah blah" nonsense, i'm not even going to bother addressing that kind of totalitarianism.
It's adorably naive that your seemingly racist world view completely ignores logistical facts of transportation of goods, food, and energy. Have fun with that, leave the rest of us out of it.