Hey Joaquin,
a good place to start is Mandy.com, you can find a lot of UNPAID shoots posted on that site. There are some PAID gigs, but those are rare. Stores you need to know to stock up on AC gears are B & H, Barbizon and Abel Cine Tech. Kodak is located in midtown and Technicolor is in Downtown near Houston Street. I hope this info is enough to help you get started.
Best of luck.
-Dan Lam