I think it depends on the chance that the student gets a job that is either in software engineering, or some job with a salary high enough to trigger the clause

I think it depends on the chance that the student gets a job that is either in software engineering, or some job with a salary high enough to trigger the clause in the ISA to initiate payback. I'm curious as to how legal these income "sharing" agreements are, can they be enforced by US law?