I don't know all the specifics off hand, but you can find it on the Social Security web site.
A person with no work history going back ten years is automatically not eligible. You must be a valid worker to qualify for SSI, it is not welfare, as I said and it is often confused with State welfare programs.
Is it 6 or 40 ?
I promise you that immigrants with zero USA work history are getting on SSI disability
A significant fact that has serious policy implications is the explosive growth in the number of noncitizens receiving SSI benefits in California. In recent months, the public has been made aware of elderly immigrants who rely on SSI because their sponsors are no longer capable of caring for them. However, a frequently overlooked fact is that many recent immigrants, in collusion with their sponsors and unscrupulous translators, have taken advantage of the loopholes in U.S. immigration laws and the government's inability to enforce the "affidavits of support."30 This is supported in a statement made by Ms. Doris Meissner, the current Immigration and Naturalization Service (INS) Commissioner appointed by President Clinton, and by the authors of two recent studies examining the number of noncitizens receiving SSI benefits. Commissioner Meissner states, "Sponsorship is an expression of intent, and it is one where the government assumes as a goodfaith matter that if a family attests to its willingness to sponsor...then it will be carried out. This area of elderly immigrants is one where it is not working so well."31
http://209.85.165.104/search?q=cache:5cd60KWhtmQJ:www.pacificresearch.org/pub/sab/health/welfare/welfare.html+%22SSI+disability%22+chinese+immigrants&hl=en&gl=us&ct=clnk&cd=4