Preferably First Floor, 500-700 a month with a nice layout . Bedroom, bathroom, living room. This is for an elderly woman , so keep that in mind.

You may also want to check PW and craigslist

Unless you plan on renting with someone, the rents not going to be that low.

where you find a one bedroom for that low is somewhere you wouldnt want to live

Check out the Presbyterian Homes at http://www.presbysinspiredlife.org/communities.html
There are a few locations inside of S. Philly, not sure of how many vacancies they have but it's worth a shot for you to look into. Even if she didn't land a first floor space, these are designed for the elderly. We know a few who have moved into Jackson Place and have heard so many fine words from them and their families. St. John Neumann Place should be completed soon as well, another fine option for our local Seniors. Good luck.