Any knowledge that I've picked up is through friends (word of mouth) the Internet and two first class books, one of them being the RHS Encyclopedia of gardening, which I strongly recommend. I did have the good fortune to have been given these books by a family friend.
For me personally THRIFT is a major factor, and the rewards are fantastic.
But how far can you go towards actually living off it would take a lot of labor, so I’m quite interested as to how fruit and vegetates will be grown with new technologies being invented. I mean, there are things you can do to contribute to energy saving buy installing solar panels etc, but will technologies such as hydroponic systems help someone such as a small holder be able to yield enough produce to feed themselves? their family ? or maybe even their community ? and this is a subject I need to educate myself on.