Never pre-pay for work, especially with a new OFS. 
Don't pay for their internet or laptop or medical expenses.
An OFS asking you to prepay for work is a big red flag.
However, there is an exception to this rule. I'll tell you what it is in this episode.
If you want to learn how I hire people who don't ask to be prepaid for work, go to https://www.onevaaway.com/