I've had some friends live in Northern Liberties and it has definitely boomed a lot in the past few years. It's pretty trendy with a lot of restaurants, bars, newer development and you can walk to old city from there or hop on the subway easily. Center City is great and I've never had a problem since I've lived here. As long as you don't look for trouble or go out by yourself at 2AM you should be fine There's affordable housing in really all of the neighborhoods if you surf Craigslist religiously like I do! If you are looking for night life, I recommend Old City, Northern Liberties, "Midtown Village" or Rittenhouse. For quieter living, Society Hill, Queen's Village, Washington Square or Fitler Square. I've never lived in the Fairmount area but I've heard good things. I also have some friends that live in south philly/graduate hospital area and love it there. Usually a bit cheaper housing but they do bike almost everywhere and don't rely on public transportation or walking.