I'd like to record some of the stuff I play on guitar, but have no idea where to start looking for microphones. I'm hoping that you guys can make some good recommendations based on my situation:

I play mainly acoustic, but I'd like to be able to record electric with distortion and stuff.
I use Audacity on my computer, so whatever I buy will have to be able to connect to my computer's microphone jack. I don't really care if I can't use my mic for performances.
I'm pretty poor. I'd like to buy something for under 50 dollars.
You can generally find used SM57's floating around for about $50. You shouldn't have to worry too much about the condition, you have to put some effort into breaking one.
ESP LTD EC-256 and a Fender Deluxe VM