Let's say after FA, remaining balance is 20k. How do I pay?

Hold it. Rutgers does NOT guarantee to meet full need. It is very possible that transferring this money will not net this student a penny more of need based aid.

Right now, I would suggest this student get all his or her other applications completed. Unless the Rutgers admissions offer is an early decision one, this student can wait,mand see his or her actual financial,aid offers, and net family costs.

Opening a 529 is a good idea.