You are only eligible for social security disability if you have enough work credits and are still insured for SSD. You generally need 40 credits with 20 credits earned in the last 10 years ending with the date you became disabled. Your date last insured is the last day that you are eligible for social security disability benefits. As a general rule of thumb as long as you have worked 5 of the past ten years you will usually be insured. There are exceptions and the rules are different for younger workers. The younger you are the less years you will have needed to work in order to be eligible for social security disability. You can obtain your work history from the Social Security Administration by going to https://secure.ssa.gov/apps6z/isss/main.html . Here you can find out how to obtain your social security statement which contains your work history.
For SSI you need both limited resources and limited income. It is often obtained by individuals who do not have the work history necessary to obtain SSD benefits. The resources you may own are very limited. For an individual you may have $2000 in cash. A couple may have $3000 in cash. You generally may own a house if you live in it and a car that you use to drive to medical appointments.
If you are uncertain whether you have enough work credits to qualify for SSD and have limited resources and low income then apply for both. You will not be penalized by applying for both, but there may be issues if you are eligible for SSD and fail to apply for it within your last date insured period. You will also not be penalized for applying for SSI if you are uncertain if you have enough work credits to qualify for SSD.
If you need help call a Buffalo Social Security attorney at 716-831-1111.