Yes, Coco, SSI is a form of welfare. It's available to people who never worked a day in their lives and paid nothing into the system. However, it's basically federal, not state, money. States can add a bit to the federal benefit, and rich states - like Connecticut and New York do - but the basic SSI benefit, for a person with no assets and no other income, is $735. That's what the federal government will pay to any destitute elderly person (or younger destitute disabled person who didn't work enough to get SSDI.) That is true in every one of the 50 states. So SSI is unearned money, but it is paid by the federal - not the state - government. Some states (most actually) will also add a state payment to anyone getting SSI. The richer the state, the more they add. Here's some sources:

https://www.ssa.gov/ssi/

https://www.ssa.gov/ssi/text-benefits-ussi.htm

When you apply for SSDI, you are automatically also applying for SSI.