Mentos,
I'm currently under going a similar situation and thought maybe I could offer you some advice. Unfourtunately, my school does not have a well-established greek system, we've had difficulties in getting more guys interested in founding with us. Because of this we've decided to start a local to use as a stepping stone before we colonize our respective fraternity. This allows us to establish by laws, a brotherhood, and it also gives us a presence on campus. This is just an option you might want to consider, once the local has taken off with success the transition to a colony is much more smoother.
The points brought up by PnguinTrax and shadokat are very valid. The national fraternity has the most to lose if the colony fails. In one of my talks with the director of expansion for a NAIC fraternity, he told me it costs approximately $6000 to setup a colony. Also, if you look at the program, it has a defined scheldule for completing the goals: e.g. XX amount of dollars raised by XX amount of days.
I hope this was of some use to you. Please keep me posted about the progress of your group, lates.