Graduate School Q and A
A: Just like many other answers, this depends on whether you get a Master's or a PhD. A 1999 survey by APA 69% of all psychology graduate students were in financial dept (related specifically to graduate school) and of those, 39% were in dept more than $51,000.
That's a lot of money, but it's nowhere near the dept accumulated by most medical or law students. And please don't forget that many graduate students are able to get financial assistance in the form of tuition remission, fellowship stipends, or assistantships (teaching and/or research).
You can actually get full tuition remission and stipends for teaching or research that allow you to come out of graduate school without any dept! Seriously! When you go to graduate school, the more you focus on school the greater your chances for success. If you have to work another, outside job that's unrelated to school, it makes school much harder.
And don't forget that you'll actually have to live while in school, which means rent, food, etc. In fact, much of the dept that graduate students accumulate comes from their living expenses and not from direct school expenses.
So make sure you ask schools what they offer and what's required to get financial assistance. Many schools give every student admitted financial assistance. This is one reason there are so few openings in graduate programs (when I went to graduate school they accepted only 2 people into my program - no, that's not a typo :).