Most universities are need-blind for admissions (which can either be good or bad based on the situation, probably not what you wanted to hear though). Some of the colleges on your list do give financial aid but that’s considered after you get in so I wouldn’t rely on your financial situation for admission, especially to the top tier schools like Stanford or Brown. I don’t know of any schools that give low-income students an advantage since most are looking to build up their academic reputation. Sorry if this isn’t what you were looking for, but it would be greatly appreciated if you could chance me back!
http://talk.collegeconfidential.com/what-my-chances/1820147-but-srsly-what-are-my-chances-of-getting-into-stanford-ps-will-chance-back.html#latest
Good luck with college apps!