Master's programs that are online, self-paced, and tuition-free?

In my research, it seems like there are a lot of online degrees, though not as many Master's degrees as Bachelor's of Associate's. Of those, only some are self-paced, and only some of those seem to be affordable or tuition-free. I've seen stuff like University of the People, or courses from well known universities on edX or Coursera, but I feel like every source I see is unreliable. Does anyone know of an institution that would let me complete an online Master's degree on a flexible schedule and on a budget? Ideally, I want to be able to complete a degree slowly and flexibly while working a full-time job and being able to save my money.