Don't underestimate the willingness of third world families to send their children to the US under this "fat check visa" scheme, regardless of whether they would have any source of guaranteed income.
Currently Africans are commonly paying over 10,000 euros for an illegal trip to an undetermined European country. The families raise the money for young men even though there's no guarantee whether the kid will end up in Norway or Italy (and often no further than Morocco). Compared to this, a five-year US visa for $50k would be an extremely attractive option. I doubt that desperate young men whose families are hopelessly in debt are the kind of immigrants that the US would want to specifically attract.
Currently Africans are commonly paying over 10,000 euros for an illegal trip to an undetermined European country. The families raise the money for young men even though there's no guarantee whether the kid will end up in Norway or Italy (and often no further than Morocco). Compared to this, a five-year US visa for $50k would be an extremely attractive option. I doubt that desperate young men whose families are hopelessly in debt are the kind of immigrants that the US would want to specifically attract.