In January 2005 I started a full-time job writing math questions for tertiary entrance, and for secondary and primary school students – on reflection, though, it was a mistake to work full-time, as I was nearing the end of my PhD thesis. I submitted my thesis in April 2005, and in the two months before submission I was effectively doing two full-time jobs – it was insane! I was working in a new fairly full-on job during the day, and then going to uni and working till about midnight on average (a few days I worked till after 1am).
Don’t do it! While we all need money to live, you need free time to study, especially when you’re completing a thesis. At most, work part-time if at all possible.