My sisters perform and were wondering this very thing when purchasing equipment. The Shure SM-58 was the one that was recommended most by the performers they questioned. When they went to Long & McQuaid (a Canadian Music Store with several locations) they were told that this was probably the best microphone for them, but they suggested renting the Shure and some others that they also thought were pretty good. This way they could get a "test Drive" The rental rates were ridiculously cheap. They ended up with the Shures anyway, but were able to make an educated decision.

Rick Fielding suggested looking in pawn shops for these mikes. My sisters had already purchased theirs new, but apparently these are so bullet proof that buying used ones shouldn't be a problem.