Excellent opportunity.
The bump in pay compensates the gas/driving.
Clearance be it Confidential, Secret, Top Secret or variants thereof are good Resume Bullets and aren't easy to come by. It's not that they're hard to qualify for, but that there are not a lot of opportunities in which a person can obtain one.
The experience opportunity compared to your current position is a forward move.
Considering the criteria you've mentioned, your current financial obligations, age and career position I'd say it's an opportunity which you should seriously weigh in on.
Very likely you won't have an opportunity like it again (and the $15.00 is starting intern salary - that's exceptional for internship. Full time status + benefits should be well worthwhile).
Good for you!