Approximately 2 females could fit in a 5 gallon happily, which isn't even enough for the minimum to have a peaceful sorority. They'd probably kill each other. Rather invest in a 2G, invest in a 10G, wal-mart sells (JUST THE TANK) for 12.99, check craigslist, and second-hand stores as well as yard sales. I got a 55G, for free, including, lights, filter, gravel and decorations, no header but hey, it was free! If you're uncomfortable going by yourself to pick up a tank, take a buddy.
Make this a goal, not a weekend project, buy the tank, then later buy a heater, then gravel, plants etc.. No need to break your wallet all at once. =D