In 2014, David Cahill, 30, graduated with a master's degree in school leadership. His diploma came with a tab for nearly $20,000.
When he entered his repayment period that November and opened his first statement, it "revealed that a 10 year repayment plan would cost a total of $27,178.23," he writes on his blog, FinanceSuperhero. "In that moment, I was determined to ensure that my $18,000 educational investment would not become a $27,000 one!"
What's more, the Chicago-based millennial owed more than $5,000 on his undergrad student loans. "I couldn't help but realize that I had taken on way more than I could handle," Cahill tells CNBC.