Yeah, yeah, I know.

I would like to learn to ride a bike. What is the best way to go about this while keeping entry costs low? Should I buy a cheap bike on Craigslist? A kids' bike (I am 5'0")? Or would it be okay to learn on a friend's bike, even if that friend is slightly taller than I am? I do not want to shell out a bunch of money on a bike when there is a strong possibility that I will skin my knees, pout, and resign myself to driving (actual process that occurred 20 years ago).