My friends and I are about to lease an apartment in Philadelphia. The owner wants to charge us the first month, last month, and an additional two month security deposit. Can they charge that much or is the last month also considered apart of the security deposit.

They can pretty much charge what they want, as long as they are disclosing that to you from the start. What YOU need to find out is how you get that money back when you do decide to vacate the residence. And make sure you retain a copy of ANYTHING you sign, don't accept a "verbal" agreement, get it all in writing!