Who is eligible for HUD or section 8?

i am in a very bad situation. my dad drove my mom mentally insane so she left him. i live alone with my dad and i am suffering depression b/c of the person he is. i may have some kind of mental health problem. i dont have a job and neither does my mom. my mom has no unsurance and she is living with my sister who just had twins and is on WIC. i want to get out of living with my dad but my mom has no money or a job or car to get started. my mother has emphizima and has trouble working. my mom needs a place to live b/c there is no room for her where my sister lives. so basically im asking what can me and my mother do to get a place to live? can anyone from the govt help us? if so how? and if it is possible we would also like to get my newborn nieces and my sister out too because the father is an illegal alien and does not help any situations. please someone give me some advice HELP!