Everyone should be aware that the IRS has a couple of excellent plain-language publications, which are free, covering nonprofits. One is on getting and keeping your exemption, and I think it is Pub. 557. The other one, which is important, is on the unrelated business income of exempts. If you don't follow the rules, there could be a lot of tax. See
www.irs.gov, where you can order or print these out. Pub. 557 might be a bit too long to print out. Following 557, it is easy to get your 501c3 status.