Some advice (again, assuming you go this route; not saying you must/should):
1. Try to find a not-too-expensive, non-flagship state school ($5-9k / semester for a full course load is a good ballpark. You can bring that down a lot by doing gen eds at a community college and then registering for 1/2 or 3/4 loads for the semesters you're enrolled at the uni. Most state schools let you pay by credit hour and are good about accepting Community college credit, but make sure you get a commitment from the uni that they'll accept any CC course you take.)
2. Get in touch with an admissions person and request a one-on-one.
a. Make sure they know you're an "adult learner" and, if you can't arrange your other obligations to take day-time courses, figure out if there are evening sections of every course you'll need to graduate.
b. Inquire about scholarships, grants, and subsidized loans. Talk with your family and figure out what you feel like you're able to afford. Be frank with the admissions person about financial realities.
c. Request a one-on-one with a faculty member from the CS department. Many teaching-oriented schools will entertain this, but don't be surprised if you get turned down. If you get a meeting, start off with general questions about the faculty's expertise in security (actually this doesn't matter so much because you ultimately want a job rather than a research position, but technical stuff is a good way to break the ice). Then ask that faculty member about what the department does to help place students in internships/jobs. As an added bonus, in general, faculty are more likely to give you a good sense of the quality of the school than admissions people (who are, after all, salesmen).
3. Don't be afraid or too proud to avail yourself of free tutoring etc., and try to be a participant in the department's community (e.g., attend official department events whenever possible. In general, be seen and excel.
4. Once in CS courses at the uni, be sure to stand out and that your profs know about your interest in security and prior IT experience (great way to get leads passed your way).
Other advice regarding finances:
1. If you have to take out loans, make sure they're subsidized. Make sure that increase in lifetime earning balances out the full cost including interest. As a good rule of thumb, the total is approximately the cost of a new, low-end car. I.e., limit yourself to the amount of debt you would put into a consumable. Rationale: education has far better pay-offs than a car, but more risk.
2. If you can xfer courses from a community college, do all those before enrolling at the uni. In the mean time you might find a good job (at which point you can choose to attend the uni or not).
3. Make sure your family is 100% on board and that you're confident you will finish the degree or get a job out of it. Be aware that, esp. if you're working during school, the time commitments and stress are going to take a toll on personal relationships.