you can buy a paper quick-trip ticket from the septa key machines for $2.50 valid for one ride on the subway (not on buses or trolleys). its listed here: https://www.septakey.org/info/fare-products

broad street line stops around midnight, but the night owl buses keep going. They aren't very frequent though. $2.50 cash fare on the bus, no change given.

Not sure what line you were asking about for regional rail, check the posted schedules, they don't run very late.