how to pay for college if financial aid doesn't cover everything

Email student services and ask about off campus housing. Sharing an apartment off campus and cooking for yourself with shave off 5k at least - Nicholls is in a small town and rent is relatively cheap + cooking for yourself will save you a lot of money.
COA typically includes books, so instead of buying them rent them or buy them used or use the College library reserve.
I agree that it/security will have a much better ROI than a general business degree.