What should I do?

I would start at a community college. It's much cheaper than a University. When you apply, you'll need to fill out the FAFSA financial aid form online. You may be eligible for grants or student loans. You can also contact the school, as most schools offer their own scholarship program as well. Tuition costs are broken down per credit hour on each school's website, or you can contact their financial aid office.

With a community college, they won't care much about your highschool GPA. They'll just want to know if you graduated, or have a GED, and then you'll either take the ACT/SAT or a placement exam at the school, to see where you stand in math, english, and reading. Afterwards, you can start your pre-req classes, which are generally college algebra, english comp 1 and 2, psychology, biology, microbiology, anatomy and physiology, and a couple electives. Some schools also may require sociology, nutrition, or chemistry as some schools differ on requirements. Check with your school's nursing department for what courses they require. It's your pre-req classes that you need a high GPA in. It's your GPA that'll be one of the deciding factors in nursing school acceptance.

First step I would do is schedule a meeting with an advisor in the NURSING department. Not a regular academic advisor, but one that's actually in the nursing department, and speak with them about your plans, questions and concerns. They are one of your best resources.