I like that ‘discretionary’ part - that means that if you spend all your money on a home and car you couldn’t afford if you were actually making the payments you should, your discretionary income will be so minuscule that you can get the 10% for the loan payments from under your sofa cushions.
I assume that there will be formulas students have to use. Still, I had to pay my school loans back and I did. My daughter is paying hers back now. Those coming after us need to do the same instead of looking for me to do it for them. If they can’t afford school, get a job first and go later. Or go to community college. Or do both.