If you live in state for a public university when your child applies and is admitted but sometime after they matriculate but before they graduate you move out of state will their tuition typically change to out of state? On what would a college base this change - does FAFSA ask for address or is there other information you would provide that would show an out of state address that could trigger this tuition rate change?
It depends on the state or university.
In some cases, residency is checked only at initial enrollment, and retained if continuously enrolled (except summers).
In some cases, residency is checked every term.
In some states, a student who graduated high school in the state after a sufficient period of enrollment may be eligible for residency or equivalent for tuition and financial aid, even if s/he otherwise would not have it due to parents moving out of state.
Commonly, universities have their own forms and procedures for residency checks and changes.
You will need to check. IME this has been OK but it is going to vary state to state, school to school.
FAFSA does ask which state you claim to be a resident of, but of course it is self reporting. I moved when my daughter was in school, and while it was a private school she did get state residency and merit benefit. There was no change in her aid. She kept her driver’s license and claimed her residency in that state.