It seems short-sighted to leave the cities, where you have a job that doesn't pay enough to buy cooking fuel... and go back to the countryside, where you won't have a job + can't afford either food or cooking fuel.

I guess you can take the time spent not working to search for firewood to use as cooking fuel, and maybe forage for food to eat. That's great until everyone does it... in which case foraging for food becomes really difficult and everyone quickly burns up the supply of available firewood.