when the money starts rolling in

... then it's time to celebrate.

When your song has become famous, is produced on CD, and is being played on radio stations, then it is time to make sure that your share of the big profit finds the right pocket, i.e. yours. Radio stations, discos, shopping centers, and other establishments where your music might be played are not prepared to provide for different agreements for each song they wish to play, which would require millions of individual contracts. Instead, agencies handle that - for all musicians. To retrieve your share you have to become a member of your homeland's agency. You need to do this only after real money is involved, no need to pay membership fees if there is nothing to gain. For Germany, where I live, this would be the GEMA. In the USA it's the ASCAP.

So, why am I not a member of the GEMA? You guess!
 :-(