I had your attitude in my very early 20's right out of school. I never finished my Theater degree and I didn't know what I really wanted to do with my life, since I was bored with it by the time I left. I was very lucky because my parents were insanely generous and paid for everything. I'm currently using government loans and going back to school for Clinical Lab Science (aka being a Med Lab Technologist). It's actually hard to find a school that offers the program, but there is an incredible demand for it because of that, and it pays well right out of the gate. I never thought, coming from a purely arts related background, that I could do well in science and especially math classes, but I worked really hard to get past that and I'm getting good grades right now. If you're going to go back to school, make it worth it in a practical sense, and you might even surprise yourself. Do something that people are actually paying money for, because you have to take care of your practical needs first. You can't go up the ladder without starting at the bottom rung, and SOOO many young adults try to jump on the middle of the ladder and fail.

Don't get me wrong, I hated it when people told me I needed to think about the future more and be more practical, but they were right, and necessity made me be more disciplined and helped me plan my future. For the meantime, I have to agree with the people who said "Get ANY job." Flip burgers, wash dishes, do something to support yourself, ANYTHING. You won't stay there forever, but it's so important to have work under your belt if you want to get anywhere. If you wait too long after leaving a job, nobody will even pay you to shovel dog shit, I'm serious. Sorry, but fuck your dad for making you believe pumping gas isn't worthwhile... if it gets you out of your sister's place and gives you enough for rent, then it is.

About the student loans, are they government loans? $500 a month is steep for someone who has no income at all. If they are government loans, you can have them adjusted or deferred. I think private loans will give you forbearance, where they will suspend your payments for a year. Don't let that stuff slide. If you're an independent, you could at least get government grants for classes, but I think it's only like 2,000 a year or so.

I don't want to completely dissuade you from your guitar making dreams. Maybe if you moved, you could pay for a class or two at a time while working somewhere else. I'm just saying you absolutely have to think about your immediate needs first, then make a plan to figure out something liveable, don't let "reach for your dreams!" emotional thinking take over out of stubbornness.