I get SSD (Social Security Disability). Then there's SSI, I'm not 100% on what the I stands for, I think income but the two are completely different. With SSD, I believe it took an average of my last four years of income I made. However, I believe with SSD & SSI that there is a minimum payment somewhere around $600 where they won't pay you less than that a month. Plus it's retroactive, so your first payment should be a lump sum