I entered the CUNY system as a graduate student. I started as a T.A. in 2004 and eventually (in about 2 years) moved on to teach my own courses at Hunter college. While a graduate student (from 2004-2012) I had a graduate B assistance reward for 3 years (which entailed teaching 2 classes a semester, tuition remission, and about $18,000 a year). When not on an assistance package I would request 2 classes a semester, and a summer course. Assignments of classes came at a semester by semester basis. My job insecurity arose near completing my degree. I was denied summer teaching, in the interest of defending my dissertation (but the financial pressure didn't help), and since graduating (though appointed for a year twice - since I have worked 6 consecutive semesters)
I am only guaranteed 1 class per semester, and need to wait each semester for my total workload. I didn't receive teaching last summer, and I only picked up 2 additional courses (3 total then) this semester since (as far as I know) a graduate student may have dropped out or left their teaching assignment. I am still waiting (now it is November) to see if I have more than 1 course for the coming semester, and I have no notion of summer teaching possibilities.
So, as well as the extremely low pay, my job is insecure (and more so since being awarded my Ph.D. - the unspoken rule is that once you graduate you should be leaving within 2 years or so). The short notification for course assignments obviously affects my ability to pre-plan or restructure my courses. I often need to rely on previous material, and the financial stress has been a constant.