SSDI is a benefit from the federal government that provides monthly payments based on the amount of F.I.C.A taxes paid during your work history. Payments start 6 months after the date of onset of disability (no payments in the first 5 months). It generally takes 3-4 months to process the claim. There is no income or resource test for SSDI. Either 29 months after one’s official disability date or 24 months after one is determined eligible for SSDI, Medicare will begin.