What do I do in this situation?

I'm trying to leave home and go NC but it's even harder for me because I have Autism. It's very mild, and I'm highly functional. I've been programming since I was 9, and have thought about freelancing online while I continue to live at home, but here's the problem. I'm on a disability which my mother has put into our joint account, I was only suppose to be on the disability while I was in college but my mother made me drop out of college and stay on the disability. I've thought about opening another account online through my joint account and keeping that hidden until I need to leave (which I hope will be really soon), but I can only have a certain amount of money in my bank account(s) before I lose my disability benefits, and my mother will flip if I lose that before I leave. Any advice would be greatly appreciated.