Your situation is not uncommon (and don't be surprised if your sales tax exemption from NY turns out not to be valid either).
The basic rule of thumb is that if your organization has more than $5000 per year coming in (not profit, not after expenses, but money coming in from any source) then the IRS expects you to formalize by filing for 501(c)(3) status. That takes care of you at the federal level.
That application form is not trivial. It costs $750 and fair amount of work. But many of us have slogged through it. It just takes persistence. You can also use the advanced search in these discussion forums (try key word: 501) and find lots of good info.
Also - look into joining
PTO Today Plus
- the paid membership part of this site. As a member you'll have access to a lot of resources, including a kit to help you file.
PTO Today has been a very generous host in providing these Forums and the file exchange and other parts of the website for free. We all try to help each other and most of the discussions here are among us mere mortals - not PTO Today Staffers (although they jump in from time to time). So there are both the resources for sale and free options that can help you along.
Definitely check in with us before you decide to pay an accountant or lawyer megabucks to do this for you. Professional advice is always great (especially if you can get it donated). However, we've had folks post in the past how they were considering paying someone $1000, $1500, $2500 (which may not include the IRS fee). In my opinion, unless you have an unusual situation or lots of extra cash - it's just not worth it to spend that kind of money when you can get help here from us.
And as tedious as the application process is, it's actually also a learning opportunity. It helps you understand about IRS expectations later.