I can pretty quickly tell who's never been poor just by their responses to topics like this. If the issue was simply a matter of perseverance there wouldn't be so many heaps of poor people. It's a lot more complex than many idealistic views on the matter might suggest. A lot of catch 22's and a lot of things you take for granted if you've never had to live without it for a long period of time. Also the geography of where you live can greatly impact it. For example if you live in a very car-eccentric city, that can negatively impact how easily you can get around for job opportunities. Fact is in this economy there are more people seeking work than there are jobs. Someone who's young with little to no work experience and out of school doesn't have the advantages that many of you take for granted or don't even see that you have.
Anyways, my main two pieces of advice would be getting treatment, and not being afraid to ask other people for help. I don't know about in a city, but there is generally always someone who wants some kind of work done, even just an extra pair of hands. It may not always be easy to find, but just inquiring about trying to get some work can often result in people simply donating some cash to you. I find it helps to explain a tiny bit of your situation sometimes, but you gotta gauge which kind of person you are talking to. If you can go to any church you are comfortable with and become friends with some people there, it's always a good way to get some help. Some might have some work, some might buy you clothes and yet some might give you a few dollars for food. That's been my personal experience anyway.
There are also some programs that can help you with job seeking and job training, particulary if you are diagnosed with anything like you mentioned in an earlier topic. Those diagnosies can easily qualify you for help from vocational programs that are usually state run but required by the federal government. So even if you don't have any experience you can get some through those programs. They are designed for people in your kind of situation who want to be integrated into the workforce and be able to stay in the workforce.
For more short term though, really just presenting the best you can and following up and getting the interviewer to like you is often a good way to get something like a fastfood job. At least it's worked for me in the past a couple of times. Even if you find it hard to hold a job for more than 2 or 3 months, that's two or three months that you have some income.
But yes, stick with the treatment. It will really, really help. And again don't be afraid to ask for help. Becoming part of some community will make that a lot easier, hence why I suggested a church.
Edit: Also, if you need new clothes ever, Thrift stores are your friend. Pair of pants for a dollar? Heck ya. And never neglect food banks + food stamps. Your state might even have a cash assistance program you can apply for. You may not be living the most comfortably but you will survive with some comforts if you can manage it well enough. Also if you can find someone who likes you and you trust becoming or getting a roommate can greatly reduce expenses if they can find work or have some income. But be warned get the wrong one and they will just sit around all day doing nothing. Anyways I say this all with some experience myself. take at least some of it wiht a little bit of salt. Life is kind of random and unpredictable. So be adaptable and above all learn to enjoy the moment from time to time, least you get consumed worrying about tomorrow.