Also to me, and feel free to shoot me down for it but I'm going to say it anyway, the situation you're describing doesn't sound to me like it's about survival sex. It seems to be more about what you want than about meeting basic essential needs, or am I misuderstanding
From the wiki page you linked to
"Survival sex is prostitution engaged in by a person because of their extreme need. It describes the practice of people who are homeless or otherwise disadvantaged in society, trading sex for food, a place to sleep, or other basic needs, or for drugs"
Is school a basic need at this point? I understand that you want to go to school to improve your future prospects, but is it essential that you do that now if you can't afford to? As others have said, a record for prostitution is going to f*ck up your prospects a lot more and given the state of your mental health, I don't think it's just your career prospects it's going to f*ck up.
I also understand that you are in debt and there is the potential for this to turn into a survival situation, but it doesn't sound like your there yet (apologies if I'm misreading that). There are millions of people are, most of them wouldn't put this on the table as an option, that's not judging those that do, just pointing out that there must be other ways around it because it's not an option for most people. I'm sorry, but I dont actually believe that this is the only viable solution for you.
Have you sought any debt advice from anywhere? I'm not familiar enough with Canada to know about it there, but there are agencies and charities over here that would help you look through your options.
Is moving to cheaper accommodation an option and making cuts there?
I know you've mentioned disability and you've said it takes a long time to get processed. I'm not clear if you've actually applied for it yet?