Wow, seriously? You are only 15 years old? It's good to know that instead of hanging out with your friends and partying, you have just decided to do something worthy out of your time and work online. I have so much respect for you now.I'm only 15 years old, and I manage to make a few hundreds of dollars per month. An online job is definitely going to save you up money, because you don't need to go anywhere, you are there sitting in your room and just doing whatever you need to, also as for the food you have food in your fridge, so you can pop up to your fridge whenever you feel hungry and just don't spend money on any fast foods and do yourself a sandwich instead.
Oh, really? I'm also planning to write a fantasy novel for teenagers/young adults and obviously I would love to write a trylogy like the Lord of Rings, but literally not as good, haha. I don't know about the whole idea yet, the place where the action is going to take place is the hardest to come up with, in my opinion.
Oh, I love fantasy novels as well, I am actually a Game of Thrones fan. Anyway, best of luck with that!