The first thing I would do is some research. Check out schools you would like to attend and find out just how much work you would need to do in order to apply there for an English Master's Degree. How many undergrad courses would you need to take? Some universities will accept a certain amount of work experience instead of course work.
Then look into what money is available in the various graduate programs you'd like to attend. I was in grad school for a total of six years, two for my Masters and four for the PhD that didn't happen. Only in the first year of my MA program was I *not* a Teaching Fellow or Teaching Assistant, with a stipend and some amount of tuition remission. And at the school I went to next, even first year MA students had TAs.
Now, it takes longer to finish a program if you are teaching, because you usually give up taking one or two classes a semester in order to teach. But you gain valuable teaching experience. I was a TA at two different universities, both times in an English department. Unlike some other disciplines, where the TAs run lab and discussion sessions, I was pretty much in total charge of the class, having to make lesson plans, plan paper topics and quizzes, grade everything, and at one university, I got to chose the books I taught. There's no professor to "assist"; you are in charge of the class. It's great experience, but it can be time consuming especially that first semester.
The TAs are usually not based on financial need, but given to grad students who are doing well in their programs. So you might be able to cut down on the amount of money you would borrow from this relative considerably. At one school, I got free tuition and a stipend when I was a TA, and some degree of health insurance. I still needed to pay fees to the university and find the money for living expenses (rent, food, utilities) and books. And there can be a lot of books per course for grad English courses. But getting free tuition helped a lot. Every school is going to be different in how they hand the TAs, so you need to find out what the facts are at the schools you would like to attend.
There's also differences in cost between attending full-time, part-time, and just taking one night class a semester. It might be worth going in and talking with someone at your top choice schools to see what all the options are.
In other words, I think it would help to find out exactly what the costs would be and what options there are for stipends and tuition remission before even starting to make a decision about this.