From the Model Mayhem FAQ:

How do I look for paid work?
There are a few ways you can look for paid work:

  1. Go to the casting call search page, and search for casting calls in the location of your choice. You can narrow down casting calls that are offering paid work!
  2. You can also post a notice to let others know you are accepting paid work. They will be able to browse your notice and will contact you if they want to hire you.