SSD, or Social Security Disability, requires you to pay in order to be insured for full benefits. It doesn’t matter how much you make, or if you win the lottery, you are guaranteed to get your full benefit no matter what. It’s unrelated to your financial status. SSI or Supplemental Security Income are for people who are disabled but haven’t earned sufficient work credits for disability services but are financially eligible, meaning they have less than $20,000 in the bank and no income. They will investigate your financial situation as well as those you live with. You get a welfare benefit if approved. The only thing SSD and SSI have in common is that you have to be disabled for both.