Alan Gould wrote:
[...]
A lot will depend upon your own interpretation of self-sufficiency.
If
you mean total s-s as practised by Robinson Crusoe (until Friday)
then 9 acres could maybe support two or three people at subsistence
level.

If you intend to raise and sell produce to pay for purchases, 9
acres
in a mountainous area of Spain worked as a commercial smallholding
could provide for a small family or group. At least fuel should not
be a problem if full use is made of solar energy.

The kind of thing you have in mind is practised in Spain at the
Sunseed Desert Technology unit, website http://www.sunseed.org.uk/
(already given by JennyC) Sunseed take in students on a work for
keep
basis, but they usually have a long waiting list.

I'm pessimistic about 9 acres of mountain land. I don't know anything
about the quality of the land, of course; but is it good enough to
grow cash crops? And if it is good enough, is it near enough to a
good market for those crops?

(Please, no goats: you'll be sorry. They don't live on grass.)

Mike.