The exact term "top 100 songs" (with quotes) gets 550k searches per month with an average CPC of $0.29 and an estimated ad cost of $42.25/day.

Satisfying anyone's morbid curiosity, without the quotes the term gets 1 Million searches per month (apparently exactly one million if you ask Google, and not one more or one less).

Google Checkout or Escrow.com (your choice, we'll split fees).

Any questions, just ask.