Math Adjunct Professor positions and salary in a big city
30% of households in Manhattan have an income lower than 36k, according to census data; 36k is actually above the average income for an African-American or Hispanic household in Manhattan.  You're right that it's hard to get by on that amount of money, but plenty of people manage it.

EDIT: A good point in the comment below:  typically graduate stipends are well below this number (31k is the highest I have ever heard for a graduate stipend in math; I'm sure the CUNY stipends are much lower). Of course, most people don't want to live like a grad student forever, but it's not as though it's impossible to survive.