Have you ever sold a song? Making money as a writer...

I read the post titled "Songwriter Question" and a thousand questions came to mind.

It covered some basics of how to find a publishing company. What I would love to know is...

Has anyonme out there ever sold a song? What is the common practice and what can one expect? Do you sell the song or do you "lease" it to someone? How does this work? I can imagine selling a song outright for say $5000 and then along comes band X and sells 5 million copies in singles and album sales combined. Even if you got a nickel for each copy sold you would still be sitting in dough. That nickel per would be worth $250K. Of course, this seems so unlikely I cannot imagine but then again it also seems kind of ideal.. from the writers position at least.

Can anyone with experience give a short explanation of what you have gone through selling or licensing an original song? Have you made money and how did you do it?

Thanks,
Wiley