I have done this. I initially applied part-time, and upon acceptance, I really dug into what would be expected of me. I decided to go full-time because of the funding package, and my decision that I could handle working part-time and school full-time. I've just finished my first year of a 2 year thesis program (first year was courses) and while it was challenging, I don't regret it. I am excited that I only have one year to go! It was manageable if you are good with time management and your work situation is fairly flexible.