I was thinking recently about how much energy it takes to set up such a natural system. In community organizing, the simplest version may be the revolving fund. Money goes into creating a self-sustaining system, and as it gets paid back, more systems can be created. But administering a revolving fund is not easy, much like agriculture isn't easy. But, in some sense, it is more likely to result in self-sustaining systems than a grant is. A grant gets spent, and nothing is left but some finite improvement. But a successful revolving loan fund continues to make improvements.
This is of course the primary reason capitalism spreads. The mechanisms for sustainability, from a captial perspective, are quite advanced. However, although the mechnisms act as an engine of growth, the results are completely inequitable.
One thing that bothers me about self-sustaining communit centers, is that it isn't clear to me where the "loan" comes from. The purchase of a "tangito", our coin whose value is one Milonga entry, is a loan to the Tango Center. If we sold 1,000, we would have $5,000 for capital improvements. If we sold 10,000, we could buy the building. In a way, this is the mechanism the government uses to finance growth, through the sale of bonds which will be repaid through future income.
A typical approach, for a community center, is to sell memberships, which are in any case required of non-profits. But memberships don't quite accomplish what a loan does. They should be instead considered a way of having your voice heard within the organization.
With the new workspot.org project tool, I hope we can create something more subtle, where people can make loans to a project, like the Tango Center, which are small & immediately paid back. This is much more reasonable than asking for pledges (although we'll have that mechanism too), because it doesn't really lose anything. Assuming that the community guarantees the loans, and has incentive to make the project a success.