There is never a reason to pay money up front, it will be dressed up as insurance, registration, all sorts,
but no matter what its called, it all amounts to he same thing, we have your money, we dont have to find/give you work.

These companies hard sell is usualy to insist you need to pay this fee by a certain time, because there is a job waiting, and then tempt you with amazing figures, yet when you step back and think about it,

1, there is nothing to stop the client (if he existed) from canceling
2, if you pay money into a bank account, its gone for good
3, if they are going to take a cut of your clients fee, they wouldnt need any money up front