There are so many qualified applicants that admissions to professional programs must be a negatively selective processes (accepting people based on having made fewer mistakes rather than on having more accolades or positives). He might get in regardless (if he takes full responsibility) but it will definitely have a negative impact at any school. Period. Ideally your app paints you as an ideal candidate; someone caught cheating is certainly less desirable than someone who hasn't. Probably not equivalent to getting caught cheating on an exam but still not good.
Help them out or something but actually give them your HW? It plainly demonstrates questionable decision making.
Since this is recent it will hurt more. For someone who has time in this situation, a few years of exemplary behavior and the ability to demonstrate growth before applying will significantly lessen the impact.