There's a difference between GETTING a credit card and USING a credit card. I've got the Delta Amex, which simply requires you to use it once to earn a 17,500 mile sign-on bonus (plus a free companion certificate). I've also got a NW WorldPerks Visa (20,000 sign-on miles after $500 in spending).

I respect your very responsible decision to avoid taking on debt in light of your present situation, but you must still be buying gas/food/etc. You might as well get something for the spending you are doing in any event.