Some sensible guidelines in taking loans for graduate schools are provided in this WSJ report- debt repayments should not be more than 10% of discretionary income so that money is there for high food, housing costs and savings. Debt should not exceed the first year's salary whn starting to work.
And students considering grad school need to be aware that while they are in grad school their undergraduate loans can grow by 50% from say $27,000 to $41,000.
47.3 million Americans carry 1.777 trillion in student debt, of which federal government is 1.693 trillion, growing at $48 billion a year. The average debt per person at about $40,000 default at about 5%.