Art Brut, both the artists and the Art!
There are things the mentally impaired can do to make a great living. There is a form of highly saleable, rare art called ART BRUT. (a movement, born back in 1945 )  The idea of "Art Brut" appeared around 1945. Its conception is generally attributed to the French painter Jean Dubuffet who meant by the term "works executed by those immune to artistic culture in which imitation has no role; in which their creators take all (subjects, materials, transposition, rhythm, style etc.) from their own individuality and not from the base of classical art or stylish trends". One can understand from this definition that parctitioners of "Art Brut" are mentally or socially marginal: prisoners, patients of psychiatric hospitals or other institutions, originals, solitary beings, condemned, all individuals who have a social status removed from the constraints of cultural conditioning. American artist Basqiat comes closest to this definition in the mainstream. He was nuts but free. However, anybody with paint and a board could imitate this non-tutored art without effort. Why? CUZ ONE IS UNTUTORED. They are looking for the 'fresh take.' The non-artist would HAVE IT, automatically.

But, if you're insane, it's even better. More authentic. If you've ever been locked up and it's on record, your gallery publicity will bring crowds of buyers.

Jean Dubuffet (1901-1985), a wine merchant until the age of 41, coined this term (Raw Art) to describe a collection he was building of works made by untrained artists. These people, he felt, were free of the deadening effects of the academy and social conventions -- especially visionaries, prisoners, children, the insane. So the movement was subversive in terms of its rejection of received notions of art. The works were physically attacked at a show in Paris in 1946. In 1948 he and Andre Breton of the Surrealist movement established a non-profit company to study and collect Art Brut. They celebrated, for example, Adolf Wölfli, who spent thirty years working on an enormous autobiography in an asylum. The terms "Outsider Art" or "Visionary Art" are sometimes used in conjunction with Art Brut.

    The Cow with the Subtle Nose (1954). (Google it, there are many online)
    Inspired by the discovery of Lascaux cave paintings in 1940, and by Paris graffiti captured in photographs, this naïve, goofy, but friendly work breaks from the European tradition of bulls in art symbolizing fertility or macho heroism, such as Picasso's minotaurs.

    Jazz Band (Dirty Style Blues) (1944)
    This graffiti-like frieze involves rubbed and smeared random colors.

A kind of primordial sludge is characteristic of Dubuffet's early works; later, he is influenced by the style of doodles, and the works become puzzle-like. GOOGLE IMAGE some more of his works.

Dubuffet counted among his friends the playwright, mystic, and one-time surrealist Antonin Artaud (1896-1948), who also understood madness first-hand. Art and writing became Artaud's method for defying his insanity. For example, he created self-portraits by charging the paper with crayons, typically breaking them.

Madge Gill (1882?-1961), was an illegitimate child whose ashamed mother hid her away for many years. She became an English housewife and spent nearly all her life in London. At age 37 she began to draw: "I felt that I was very certainly guided by an invisible force, without being able to say what its real nature was." She decided she was a medium, guided by an unseen spirit she called Myrninerest who was the force behind her obsessive drawings of girls' faces enclosed by intricate flowing patterns of intertwining shapes, and behind inspirational writings and enormous drawings in indian ink on rolls of material her son rigged up on spools. She tended to work in the half-dark.

Adolf Wölfli (1864-1930) was born poor in Switzerland and at 8 years old was working as a goatherd.He worked later as a woodcutter, farm laborer, and laborer in town. At 25 he showed a disturbing predilection for very little girls. He was arrested several times and was finally sentenced to two years in prison. At 31, he was sentenced to permanent confinement in the Waldau hospital, a situation that made him so violent that he spent most of the next 20 years in solitary. In 1899 he began to draw, write, and compose music obsessively, often from morning to night, for the next 30 years. Thus his output is extensive, including hundreds of drawings, stacks of writings, and musical compositions that no one has succeeded in deciphering. But there was one done in 1929 that Andy warhol must have come across. A Campbell's Tomato Soup can! Ahhh the penalties of not having a good P.R. guy.