Between 1998 and 2001, I was involved in the start-up of the Copper Star drum corps (both the senior corps, which started first, and the junior corps). I hope you won't mind, then, if I give you all some friendly advice about trying to start up a drum corps.
First and foremost, do know that this will be a time-consuming endeavor. It's amazing just how much time drum corps takes up, and the world is not the same as it was in the 70s when there were much fewer distractions. So be prepared to take this activity on as the equivalent of a second job if you're wanting to do this right.
Second, treat the organization like a business. One of the most important activities corps personnel are going to undertake, especially at the beginning, is fundraising. Do everything you can to raise money. Because this will be an adult activity as opposed to a youth activity, fundraising will be more difficult; people will donate to help out kids, but not for other adults. Expect to work hard for the money. Likewise, be creative in your fundraising. The old, traditional methods for raising money are difficult to use today (e.g., bingo). How else can you earn money? (Another thing: keep out of debt as much as possible. Use cash for all corps purchases.)
Third, accept everyone. Don't limit yourself to actual alumni of the Squires and Pages. Bring in as many people as you can. Consider various levels of commitment, a la the Empire Statesmen, who had three levels (those marching in the DCA shows being in the third and most committed level). Likewise, don't limit yourself to adults. If you compete, make the organization an all-age corps so that you can help keep the drum corps activity in upstate New York alive.
Fourth, build up the organization as you can. Don't think that you have to have a full-blown competitive DCA corps in your first season. Equipment is expensive, especially horns. Build up the guard and drum line first; those two groups have the most opportunity to perform in the off-season through WGI events. Uniforms aren't a must have, not at this time. Nice polo shirts in the corps colors will work just as well for the time being.
Five, use momentum to help you build the corps. Competition is key. You're located in the heart of DCA country: take advantage of that. Build up by performing in as many venues as possible (WGI, DCA/Minicorps, parades, other exhibitions). The more exposure you get the easier it will be to recruit; the bigger the itinerary, the easier it is to retain membership. People will drop out if there are no events coming up in the future.
I may update this if more points come to mind. Don't be afraid to ask specific questions; I can respond publicly or privately.
Keep up the good work!