If there's interfaith groups that could be doing this as a project, ask them if they'd be interested. We strongly advise that you have two separate people serve as writer and editor for all written materials. You'll need a computer with a decent database program and word processor, and access to email and possibly a web browser. You need a bank account and an initial funding source. If you start this group as a project of one congregation, that will take care of itself.
Many nonprofits start out as projects and eventually become corporations once they're stable.
Recruit an initial list of supporters. We started with ten. Talk to people you know, explain the model, have them look at our web site. Build an initial mailing list. Ask your initial supporters for more names.