Here's the deal. In general, students who already have a bachelor's degree are not eligible for financial aid to get a second bachelor's. Depending on your post-bac program, you may be eligible. If it is an eligible program, it is possible to get funding for required pre-requisites, but it entirely depends on the program and institution. I would talk with few programs around your area to see if the funding options differ.
If that proves fruitless, your best bet would be scholarships (there are some tailored to students going back to school), grants, and private loans.
Hope this helps!