How easy is it to get SSI Disability in America ?

SSI (supplemental security income) is a federal WELFARE program managed  by the Social Security Administration.  If your income and resources are within allowed limits, they will make a medical decision.

THE DECISION IS NOT MADE BY YOUR DOCTOR.  Social Security obtains the medical records and evaluates them using their criteria.  You must be so severely disabled that you are incapable of working and earning at least $1260 a month for at least one year.  If under age 55 you must be unable to do ANY work not just work you've done.  If you are age 55 or older you must be unable to do the same type of work you've done most in the 15 years before becoming disabled.

It takes 2 to 3 months to gather the evidence and make the decision.  About 35% of new claims are approved.  If denied you can file appeals.  Reconsiderations take about 2 months; hearings 1 to 2 years, an Appeal Council Review over 1 year.  That is the last decision to be made on a claim by social security.  After that you can file an appeal in the US Federal District Court.  No point in getting an attorney until AFTER you've filed your request for a hearing.

The same definition of disability applies to social security disability benefits as well as SSI disability for adults.  The definition of SSI for children under age 18 is more lenient and there is no such thing as a social security benefit based upon a disability being paid to a child under age 18.  In order for social security to make a medical decision you must have worked and paid into the SS program long enough when you were working.

SSI and social security are entirely two different types of programs.

I was a SS claims rep for 32 yrs.  I specialized in the processing of disability claims for 8 of them and continued to work disability along with retirement and survivor claims after specialization ended.

It varies. Some deserving people never manage to qualify, others who aren't as disabled seem to be able to get it without much trouble.
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Your post belongs in Government, not Immigration. You can click Edit (pencil icon) under your question and relocate it.

I am severely disabled and met the criteria for that but due to my husband's income it disqualifies me because you cannot have more than three thousand dollars in assets. So I am determined disabled but rich!! Haha 

Judith's answer is very good but she left out the part about your assets and they count any property like your car value to try to knock you off. My 1998 car is worth about five hundred but social security says it is worth two thousand. JOKE!

Start by visiting your family doctor so they can gauge the extent of your disability.  They can help you start the paperwork and provide you with information on the program.  It can take up to two years once you start the process before you get a determination.  If you do qualify then you will have regular reviews to make sure you still qualify.