Personally, I wouldn't attend either an unfunded masters or PhD program. A professor I'm close with on my campus did so, and she's really struggling to make ends meet--even with a tenure-track job.
The thing with an unfunded masters functioning as a spring-board for a funded PhD program is dicey. While it might work, it also might not, you know? That's a personal call that will vary, but I wouldn't do it. Since the job market for academics in a few years is an unknown (especially with the student debt crisis that seems to be brewing), it seems to me like getting an unfunded masters could be a major issue down the road, even with a funded PhD after.