Hi Penguin. I work in the not-for-profit sector (I'm currently managing director of a human rights organization, and have previously worked with church, arts, and educational organizations) so can help you think through this a little.
Legally creating a not-for-profit is easy - step 1 is incorporating within your state and step 2 is applying to the IRS.
The real issues are about organizing. You need to find (recruit) a solid core of people who are passionate about the issue and willing to work with you on it. These folks would form your organization's board. And you need someone who will lead them - presumably you. These are the people who will contribute themselves and ask others to contribute. They will also recruit other people to your cause.
Creating a group like this is very possible, if you have an important issue you are dealing with and there are people who are passionate about it.
Your project is very sobering to me, though. I don't know the building you are talking about, but I can't imagine its less than a $5 million project. You're not going to get there through $100 or even $1,000 donations. You would need to find some major gifts, at least one or two in the $1,000,000 + range, and you would probably need to forge some sort of partnership with the local government. This could be quite challenging.
Hope this helps. Feel free to pm me.