Go to the college now and post on the community boards you are looking for help, roommates etc. you will be surprised at the outreach you find. It will be up to you to find the best fit. Also, you will likely qualify for financial assistance if you need it for living arrangements. You won’t starve either. Aside from the ramen staple diet you will find food pantries that will help you and school programs where you can collect the food you need each week. You can do this.
If you go the sister route, do everything you can to help her. She has her hands full. Clean the house, do the laundry, walk to the store, watch the kids so she can grab a nap, bring steaks home on a blue moon. It could work and be really beneficial for both of you.
You are at the cusp of a totally new life. It can be daunting but it can also be euphoric. Weigh your options and try to do what is best for your progress.