Response A: Yes, because there would still be niches in the social fabric that needed to be filled by entrepreneurs in the agriculture field.
Response B: It depends what you mean by "make a good living" > does it mean having what you need or does it mean making 100,000 a year with a 401K?
B1: yes they would make a great living.
B2: it would get increasingly difficult as all your neighbors started meeting their own needs and you had to spend more energy, going further afield, to turn your agricultural products into cash. I suppose transport/sales over internet could help you out, as long as it remained economically viable.
But if you lived in a community where everyone was meeting their needs just fine, why would you need 100,000 and a 401K?
I think a good example of what you're looking for is the Dacha in Russia (scroll down)
http://www.underwoodgardens.com/growing-your-own-food/russian-dacha-gardening-homescale-agriculture-feeding-everyone/
Profit in permaculture is a can of worms. These hypothetical questions don't really go anywhere anyway because they hardly ever lead to directives to act.
You could also listen to Paul's podcasts called "Just Enough" about the book "Just Enough: Lessons on Living Green from Traditional Japan"
https://permies.com/t/23097/podcast/Review-Part
William
