a dac can have a work history, just not currently earning in excess of sga, and they can work while on it and are encouraged to so with some income disregard programs. in fact, in the insanely rare situation where a dac actually acquired enough quarters to qualify for ssd (vs. ssi) under their own work record then an application can be made and social security has to look and see if they will qualify for more under their parent's work record.
dac IS subject to maximum family benefits amounts but in our case dh and i both draw from our own individual records so that means ds draws on the higher of the two and it's considerably more than ssi (and he's not held to the ssi income/assett restrictions but the more generous dac).
i agree-financial planning in this situation is key. we were fortunate to have an estate attorney who was very educated in both elder and disability law so coordinating dac, life insurance, trusts, an able account...was paramount in everyone's mind.
no, prior ssi receipt is not required for consideration what so ever, in fact many young adults in receipt of DAC would not have been eligible for ssi b/c until age 18 their parent's income and assets would have made them financially ineligible. if the parent does not pass away or begin receiving social security until AFTER the child turned 18 then it's possible they may have applied for and received ssi but it is not required. the eligibility for DAC under a parent's record is (copy and pasted from social security website)-
An adult who has a disability that began before age 22 may be eligible for benefits if their parent is deceased or starts receiving retirement or disability benefits. We consider this a "child's" benefit because it is paid on a parent's Social Security earnings record.
The Disabled Adult Child (DAC) — who may be an adopted child, or, in some cases, a stepchild, grandchild, or step grandchild — must be unmarried, age 18 or older, have a qualified disability that started before age 22, and meet the definition of disability for adults.