There's two plans, both government-run but one is for those who have worked and become disabled and is part of our Social Security plan; we give money from our paychecks and, if we become disabled while working and have worked all along, etc., usually one gets some disability for awhile from one's job and when that runs out, if one is still not able to work, then one applies for SSDI, Social Security Disability Insurance, and that "continues". However, it gets a little more complicated if one doesn't apply right away or doesn't have a job with obvious disability insurance and there are rules, of course, for how long one has worked and how recently, whether one expects to work again, etc.

Then there's another plan, not Social Security, for the disabled who haven't/can't ever work or not enough to qualify for the Social Security they've paid for by working. It's Supplemental Security Income (SSI) and that's a form of "welfare" since the people who apply haven't worked and contributed to Social Security enough to qualify for Social Security. Obviously it is harder to get, especially for mental illness, as one doesn't have much to go on to tell whether a person "qualifies".

Both plans have one's doctors having to do the bulk of the paperwork, detailing the disability. The majority of people have no trouble getting SSDI but, for psychiatric illnesses, it is harder sometimes as "proving" one is disabled can be harder in many cases. In both cases the goal is to get the person working (again) and there's all sorts of special training programs, etc.; I have a good friend who's quadriplegic and they trained him to be a computer design operator (not easy when you only have limited use of your hands!) and got him special tools, etc. and get him a job, but when the economy is bad, he's one of the first laid off since he's slower than most and, businesses have to make money, that's their point, so he goes on and off unemployment (which is different from Social Security or SSI) and then SSDI when that runs out.

Like any insurance/government benefit, it does require a lot of paperwork and time and effort but not really a lawyer, if one has a clear case. The lawyer impression is our lovely legal system which is more fouled up than our government/insurance systems; they aren't doing it for free or because they're "nice"