You will need to swipe your credit/debit card, but will not be charged unless you return it late (after 9pm the next night). In that case, you'd pay $1/day for each day it's late.
Check here for Redbox locations. You can use each code once per credit/debit card.
And, check out the "big" list of free codes here. I do my best to keep it current, so let me know how they work for you!