I have a suggestion for you... if you can not afford to buy music you might check into what is known as "Podsafe" music. This is music released by the artist under a Creative Commons license. Many artists around the world are using this license now in order to get their work out and gain audiance.
Under Creative Commons license you are legal to not only listen to the music, but you may make copys of it and share with others. The restrictions mainly are that you may not use the music for commerical gain without getting a regular license from the artist.
Don't make the mistake of thinking just cause it is free that it isn't any good, there are many top name artists who do just this very thing, and a great many artists you never heard of are putting out some top notch music in just about any style you can name.
Here are a couple of places to get started:
http://music.download.com
http://music.podshow.com
http://www.garageband.com