To RA, call Residence Life and ask if it’s a possibility.
I was offered a grad assistantship to run the recitation for a large lecture. It was provided to me before committing. I did not seek it out. This is how I paid for grad school.
I was offered a role in the computer lounge at another acceptance - but didn’t choose that school.
If you can’t afford a school up front on day one, then it’s not the right school for you.
If you’ve been offered nothing, I’d reach out to the department and ask how you can secure something. And the same with housing - although I wouldn’t think it would be likely.
Good luck.