If you want to be self-sustaining and live off the grid, you'll need about 2 acres.

http://1bog.org/blog/live-off-the-land-2/

Note that the blog article doesn't cover stuff like food preservation (after slaughtering a hog, how do you preserve the meat for later eating?), or building a surplus (and storing it for long-term) in case you have a bad harvest.

Chip H.