Does having a recommendation letter from a professor of the University you’re applying to help boost your chances of getting in specifically with Ivy leagues?
It depends on the status of the professor…from some famous profs it might help, but from most, probably not. It would also depend on the nature of the relationship and if they can speak to your academic strength…if one did research for the prof that is better than from prof who is a family member or neighbor.
Also, this rec letter can not take the place of the GC or teacher rec letters. So, it would be an extra letter, and not all schools accept those, so do your research.