It has nothing to do with SSI or SSDI. Basically what they do is take your income, minus all sorts of their own deductions like rent, medical expenses, extra food expenses for food related to cf... then they find out if you are elgible. They also have a sliding scale, it's not cut and dry like "oh, you do qualify, or you don't qualify" They will really work with you. I make over 3k a month (not much in CA) and Mark gets $780 in SSDI, and we still qualify and use it for mainly the boost shakes since tricare covers almost everything else.
Julie (wife to Mark 24 w/CF)