How many work credits do I need and what does it depend on?
The number of work credits you need to qualify for disability benefits depends on your age when you become disabled.  Most of the time, you need 40 credits, 20 of which were earned in the last 10 years ending with the year you become disabled.
How is it determined if an adult "child" is disabled for SSDI benefits?
Is the child age 18 or older?