Interesting, I was just thinking about this the other day....but stopped when I realized that in the US, sustainable living communities generally need to be able to gain non-profit status....in order to be, well, sustainable. I don't know about the legal necessities in Spain though.
To answer your question.... If I were to cast all my current interests aside(career pursuits, namely), my interest would be substantial, as long as I were assured complete solitude.
Indeed, small scale communities like this tend to be fairly dependent on a
group effort, so in order to minimize group interactions, I would suspect the beginning stages of building this type of community would require a lot of extensive group work/planning...
Also, I think this idea might work better with introverts, rather than schizoids(could be wrong though...I guess we'll see when people reply)....non-schizoid introverts seem to be more "well rounded"
Blah blah blah. Sorry, you have hit on one of my interests here