Help me make a Macbook decision

I have a friend that I am trying to convert to Macs, after having become a recent convert myself. She was about ready to go with a refurbished black Mac book last week but all that has changed now. I am now looking for advice as to which way might be the best to go. My main question, I guess, as far as which model to get is hard drive capacity. When you initially purchase a Mac, How much hard drive space is taken up with everything that is preloaded onto the computer? Knowing this might make the decision a bit easier. Thanks for any advice
Joe