Encore career

Currently, I am thinking about going back to school for a graduate degree to change my career entirely. It would be hard to do this while working full-time. I think that if I stick out this job for another 15 years, I should be OK to retire. (It's just me -- no husband or kids -- and I owe about $80,000 on my house.) I would LOVE to quit and go back to school (maybe with a loan?) for an "encore" career. It's amazing how much more expensive school is now. It's crazy. I know that I will be able to find a position once I have the degree. It may not be earning as much as I do now, but that's OK. Is this even something I should entertain? Jackie, Columbus, GA