I am aiming at UAB for med school after my undergraduate(assuming I will get my green card before applying), but here is a question.
If you are going to state university, do permanent residents still pay out of state tuition?
If they are permanently resident in a different state, yes.
Every state university will have a page called something like ‘residency requirements’ (here is the link to the one for University of Maryland, as an example: http://www.usmh.usmd.edu/regents/bylaws/SectionVIII/VIII270.html). Most of them will require that you have lived in the state for some amount of time (usually at least a year), and that your living there is not solely to be a student (most- but not all- states don’t like OOS students converting to in-state fees after a year or two of attendance). There is a big range across states- it won’t surprise you to know that the states you probably are most interested in are likely to have the toughest requirements.
Seems like I can’t get in state tuition rate 
the OOS rate for state med school is so expensive! It’s around 60k.
I will ask whether if it’s possible to get an in state tuition if I graduate with GC, take a gap year and work,=
If you are already living in Alabama working for a year will qualify you as resident.
I guess I have to take a gap year then agter undergraduat3
Many students take a “slide year” anyway, a year during which they work and apply to med school. If you did that, as a permanent resident living and working in Alabama, you’d be considered an Alabama resident.