Can I leave home because of my autistic brother?
What about your brother makes you want to leave?
I've spent my whole life taking care of him, I don't want to anymore
I understand that you might be feeling a bit tired or overwhelmed by this, and it is normal to respond to that by wanting to leave.  However, rather than just leaving have you considered asking others for help taking care of him?
Tell me how to find a babysitter for him. There is no way I will leave my brother.
Being a caregiver is an amazing quality in a person, it takes so much physical and mental work and you should definitely be proud of yourself. It's normal to get overwhelmed and want to bail, but help is there you just have to find the right person. Have you considered talking to someone from your county, city or township, there are often programs for situations like this!