I’m thinking about learning to play the guitar, but I’m a college student on a tight budget. Looking on www.craigslist.org I can find some acoustic guitars for <$100, but the quality is probably not that great. How good of a guitar do I need if I'll probably buy a better one if I decide to continue playing? Does it really matter whether it's a Yamaha or Fender (or some other lesser brand), etc.? What are the *essential* things I should be looking for in a first guitar? If anyone knows, I would also appreciate descriptions of the major guitar teaching methods. 
hehe, it's nice to see all these helpful responses. ^_^ Just as a note, I've played the piano since 3rd grade, and a Chinese stringed instrument (similar to the violin) since 7th. I want to start on an acoustic because it seems more versatile if I know I want to learn classical guitar. I've been trying to decide whether to pick up the guitar or violin, but I figure it would be easier on my budget if I try the guitar first (esp since it seems like I'd be more likely to be able to teach myself guitar than the violin). If I like it, I definitely plan to look for a professional teacher. Thanks again for the responses!