There are plenty of law firms that you can call and get some advice from. I used one I saw on the Internet. Plenty of them advertise on TV. (You do have to have access to a phone that you can be reached at. Or not . . . you might be able to make an appointment to call at a certain time.) The person who screens you, most likely, will not be a lawyer, but will know a lot. If law firm, after law firm, declines to take you on, as a client, it is because they see your prospects as not that good.

Everything in the posts above is good advice, IMO. You're facing a pretty tough sell to convince the government that you cannot work. A big problem, in that regard, is that they set the bar higher for younger people. If you are homeless, you may have access to specific healthcare services for homeless people. Hook up to what you can. Any lawyer you talk to (or his/her assistants) are going to want a list of who treated you, and for how long. Also, they want a list of your meds. If those lists are all pretty short, or empty, then you might need to come up with another strategy to survive.

Some shelters offering short-term support can hook you up to longer-term support, if it seems like you might benefit from the additional investment.

What the government is going to look at is this: How big of an effort have you made to get treatment that might help you recover to where you could be employable? You may not be employable now, or ever. Still, you have to demonstrate a real attempt at trying to manage your psych problems, before they will look at you in that light. Alternatively, you have to be so lacking in self-care capability that the local adult protection services will make the case that you can't be expected to do that.

At age 30, I was homeless and unemployed and wandering across the country. I did have friends and family to give me a hand up from those circumstances. Lacking that support network, you are in a tough bind. I hope you find a way up.