Collaborating via the internet.

I have been working on a mixing project for a band based in the UK, which involves 11 songs. Communicating and finalizing the work has been challenging due to the time difference and distance, I am based on the west coast of the america, There is a concern that the band could be getting mixes done by multiple people without paying them. I am also mixing on spec without any confirmation of financial reward at the end of the project. Due to limited time, I am unable to spend too much time finalizing mixes. I am considering setting up an agency for mix engineers like me, who would like confirmation of payment for work done, even if the job is not accepted by the client. I am wondering if there is any way to get clients to commit to payment for work done or not.