I've lived, went to school in, and worked in Philly for about 20 years, so I can help you out. I commute to center city every day. I live in the burbs and it takes me 35 minutes total from my house to work.
First, if you live in center city, a car is not only unnecessary but will be a hassle with parking, traffic, etc. Riding SEPTA from the airport is slightly different. Depending on which 'line' you live on, commuting to school is very convenient since there is a SEPTA station right on campus (one on clinical campus and one on undergrad). If you live in center city near (say 15th street), you can be at the campus in no time at all.
However, if you live outside center city, then a car might be needed unless you want to take the Regional Rail or something.
Truthfully, save yourself the hassle and pay the little extra for the Center City life. It's safe, it's a nice area, and the commute will be easy and safe. And if you're from Colorado, you will really enjoy the awesomeness of city life at Center City. It's great.
Second option is to live near campus. Yes, we all know about the 'area', but there are student centric locations (mainly undergrad) that are near Temple (main campus) that are safe because it's mainly students. However, if you just live somewhere on the broad street line near Center City, it won't be an issue.
Personally, I would strongly advice against a car. You do NOT want to be dealing with traffic, and parking. You just don't. It's going to add a lot of unnecessary stress. Philly is an old city and some of the streets are narrow - do yourself a favor and don't drive.