No not really, I got on SSI and am 25 and live at my moms house...I contribute to rent now that I am on it and eat some food my mom and her boyfriend get(sometimes mostly that as they lowered my food stamps and groceries are rather expensive)...but no you do not have to be homeless with no help of any kind from anyone. The amount of help you have from others can influence the amount you get and if you're needs are entirely covered by family members or friends helping them out then you wouldn't qualify.

But yeah they don't deny people for wanting money of their own due to being unable to work due to disability(who doesn't want some of their own since you essentially need it to live these days)...they deny people for not being disabled...though of course they still deny people that are disabled considering some appeal and still get on it. But the reason to deny is if they determine you are not too disabled to work, or if you have too much income/money/assets of any other kind to qualify.