it's possible but it'll be really tough! you have to be committed to doing literally nothing except work and school. i know a few people who did it.
i will say that i've heard from yale and emory that they limit the amount of hours you can work/week (only 20/week at yale, which is about 50% FTE) -- although i'm not yet clear if that's only on-campus/school-sponsored or not. i don't know if they can really tell you that you can't work to survive but some schools seem to be less flexible (e.g., classes only offered during the day) so your school and work situation will likely need to be flexible. i think the flexibility would also make it easier on your mental health.