In order to qualify for Social Security Disability Insurance, you have to earn 40 credits (credit has the same meaning as a quarter of coverage).  Of the 40 credits, 20 have had to been earned in the last 10 years (worked 5 of the last 10 years).  For 2011, one credit is equal to $1,120 and four credits is $4,480.  The minimum amount required therefore will  vary depending on the specific years the individual was employed.

Further problems may arise due to self-employment.  The SSA has a specific policy when dealing with those who are self-employed.  The SSA has three tests to determine if the individual qualifies for disability insurance or if they have partaken in “substantial gainful activity” (“SGA”).  Test 1 evaluates whether or not the applicant has engaged in substantial gainful activity by rendering significant services.  Test 2 evaluates the work activity using specific factors in its analysis and compares it to unimpaired individuals in the community.  The last test looks to see if the work is worth a specific amount as determined in the federal code.

I have attached an article from a law firm giving a high level view of what the SSA evaluates for the self-employed (written in 2004, but still relevant), the chart used to determine earnings and credits, the Code of Federal Regulations section dealing with self-employed individuals, and the Congressional Report on the Primer on Disability Benefits.

§ 404.1575. Evaluation guides if you are self-employed.