My DD is over 18, so it went on her income only (and she has none).
SSI-Disability is based on first on the person being disabled, the person applying for it (or a parent) paying in enough quarters to qualify and also on income. I don't remember what the limits are, but you can find it on the SS website. We did not apply for DD until she was over 18 because our income was too high and we knew she would not qualify.
not to contradict, just to clarify a bit-
there are 2 types of disability benefits paid by the social security administration-ssi and ssd. ssi eligibility is based on disability, income and resources-if it is a minor applicant, the parent's income and resources are considered. ssd eligibility is based on disability and having enough contributing 'quarters' in the ss system (some types of income count, not all, and there is no resource limit)-ONLY adults qualify for ssd (although if a minor, disabled or not, has a parent in receipt of ssd, there is usualy an allotment for them as well). the only time 'quarters' come into consideration regarding 'children' is when an 'adult child', unmarried, between 18 and 22, disabled (by social security's criteria) prior to age 22, who has a parent in receipt of either retirement or disability benefits, or has a parent who is deceased applies. in that case social security will look to see if the parent has enough work quarters in which case the child may get a higher benefit by drawing from their parent's earning record.
be aware-social security excludes from consideration some types of income and resources (you can check their website for a listing).
as for medical assistance-check with your local health and social services department as well. there are more programs than you can imagine-and some have VERY high income and resource caps. if you find you are eligible but with a high 'soc' (share of cost-it's not a premium you pay, it's like the deductable on standard insurance but it's done on a monthly vs yearly basis) consider the following-in most programs the share of cost is NOT something you pay every month. you only pay as you go-so if you/child has med costs of $100 one month and your soc is $900 you still only pay $100 to the providers, pharmacy (whatever). BUT-it can be a godsend when you have a month where the bills are in the thousands (or tens of thousands)-you will only have that set 'soc' to meet (and 'technicaly' you only have to have 'obligated' yourself to meet it in most programs-so you indebt yourself to the provider for it and if necessary set up a payment plan).
one other suggestion-if you have a minor child whose disability/illness is orthopedic, burn, spinal cord injury (and some others) in nature-consider exploring a referral from your doctor to shriner's hospital. they will take patients if a doctor does a referral indicating that a child will likely benefit from their care. they do not take income or resources into consideration nor will they accept ANY form of payment or even bill any insurance you may have for any care provided in their facilities. an absolutly AWSOME organization (dd is having orthopedic surgery through them thursday

).