They say at 15 you know everything, or think you do. So I won't expect this advice to actually be followed, but I'll waste my time anyway 
Catch a female watersnake by hand. See what it's llike to raise a handful of babies before you go too far down this road. If you haven't kept herps before you might be underestimating not only the work involved, but the problems. If your cages aren't kept clean Nerodia especially will develop blisters that will kill them in short order.
What will you keep all those snakes in? Escape proof cages of what sort? And what will you do when they start developing thiamin deficiencies, as they certainly will with a diet of bait minnows?
What will you do in the fall when you don't have as much time to clean all those cages a couple times per week? And how will you pay for the babies food this winter?
I'm not trying to discourage you, just suggesting ways that you might have a better chance of success. No one "traps" water snakes, they catch them by hand - learn to do this and you'll have less chance of accidently killing the snakes with a poorly designed trap, or one that is not checked often enough.
Learn what its like to raise a small group of snakes before you try to raise hundreds. If you try to do too much right off you might end up discouraged and frustrated. Right now your imagining all the up side while your blissfully unaware of the numerous down sides!
Good luck,
Joe
http://www.HerpNet.net