Top products from r/livingofftheland

http://www.motherearthnews.com/renewable-energy/passive-annual-heat-storage-zmaz85zsie.aspx#axzz3L4TMf2D6

Passive annual heat storage is your solution. I met a guy that made his earth home so efficient his house started getting too warm because he didn't account for the extra heat generated from his appliances. I have John Hait's book and love it.

http://www.amazon.com/gp/aw/d/0615905889/ref=pd_aw_sbs_1?pi=SL500_SY115&simLd=1

You should make sure the land has year round water. You'd want to physically visit the property in the driest parts of the year (typically August/September) to see what the flow is and determine if that flow will meet your needs. Remember, you don't just want water, you want water that will meet your needs.

For other considerations (which there are a metric shit ton of), you should really get this book, Finding & Buying Your Place in the Country

The latest edition is the 5th edition. You'd want this one.

The best place for pricing is probably ebay where there are currently two for $45 with free shipping.

Here is the desktop version of your link

I think you could do it on less than 5, provided that you did not raise meat, or very little. Provided that you lived in a climate the produced most of the year, and ate only veggies and fruit I think it could be done.
http://www.amazon.com/Five-Acres-Independence-Handbook-Management/dp/0486209741/ref=sr_1_1?ie=UTF8&qid=1347587158&sr=8-1&keywords=5+acres+and+independence

I'd guess Buzzfeed isn't a scientific source at all, but there's still no harm in calling it out. I just find the whole article's presentation of "shocking water use" is misleading, the facts are overly-distilled (sorry for pun) and set up for a misleading bias.

The article credits a book 10 Billion by Stephen Emmott for its data, and it seems that some reviewers have a similar opinion of the book.