Your question should not be "Can I live off of loans?" but rather ... "What will having enoromous loans do to the quality of my life after I graduate and have to start paying them back?"
Of course you can live off borrowed money. It's the paying it back that is the problem.
As someone who spent 7 years as a full time graduate student (2 years for MSN, 5 years for PhD) ... I recommend you work for a while, save up some money, and do at least the first portion of your graduate education part time while taking advantage of tuition reimbursement. That will save you a TON of money in the long run because it will cover some of your expenses and reduce the size of your loans. It will also completely eliminate the interest you would have accrued on those early loans as you are in deferment during the later stages of your education.
Also, I strongly recommend working closely with your school and its financial aid office. They should have some traineeships and/or assistantships available for doctoral level students. Those usually provide valuable learning experience along with cash and are usually tax free. See what you have to do to qualify for one.
Remember: You'll be much more attractive on the job market after graduation if you have some relevant experience in your background. Employers look for more than just the right letters after your name. The degrees only get your resume looked at -- they don't get you the job.
llg, PhD, RN-BC