My mom is a waste of space and a nonfunctional human being

The only success my mom has had in life is being a prostitute, which consequently is how she met my dad who is her current sugar daddy. My mother has many untreated mental health issues that she refuses to get help for. We live in a country with free health care so money definitely is not the issue. She spends upwards of $80 a month on takeout food when she has a Mcdonalds a few feet away from her apartment and cupboards stocked with ingredients. She can barely afford to pay her bills because welfare doesn't give her enough money for sitting on her ass and being crazy but she still has enough money to eat her weight in Santa Lucia pasta once every week or so. Every few days she has a pissy meltdown over something completely irrelevant, like her cat staring at her. I am not kidding. Most of the time her meltdowns are over arguments we have, mainly about me not doing housework. I have a full time job. My duties are to go to work and feed myself. Even though her only responsibilities in life are feeding the cats, doing the dishes and scooping the litter she still complains about how much she has to do. A week ago I woke up to my mom calling my name at 3 AM. She went to a bar and drank so much that her blood alcohol content was 0.4% and I had to babysit her drunk ass for an hour until I finally had enough and went to sleep. Sadly she survived.
On January 1st she got drunk at a small family gathering and proceeded to yell, throw shit, cry, angrily stomp around and bang her head against the wall all while her 8 year old granddaughter was watching. There was no reason why she did this. Absolutely nothing set her off. She just wanted an excuse to act like a toddler. She's not even supposed to be around children, not because she's a pedophile or a sex offender but because she's that dysfunctional of a human being. She has successfully raised 0/5 of her kids. The one that did stay with her the most turned into a crackhead.
She rapidly cycles between hating my guts and praising the ground I walk on. Anything could set her off.
I have many more examples of my mother's bad behaviour, as does everyone in my family. The only reason why I still stay with her is because she charges me $250 a month for rent and my job is only a 5 minute bus ride away.
What should I do about this?