The federal public service loan forgiveness program (PSLF) allows students that make 10 years of payments under a qualifying plan as an employee in the public sector to forgive their loans. One must use ICR (income contingent) or IBR (income based) plan to qualify; Under ICR = 20% of your discretionary income; the monthly payment under IBR = 15% of your discretionary income.
So how is your discretionary income calculated?
IBR: AGI - 100% of the poverty level
ICR: AGI - 150% of the poverty level
The poverty level is national, unless you live in Hawaii or Alaska. Cost of living and salary is local. Don't use my SF salary against a Nebraska poverty level to decide how much I can afford each month.