@Antonia436 The fees that a primary host chooses for their listings are totally separate from the payment arrangement they make with a co-host. There's not really an industry standard for how co-hosts get compensated; it really depends on how many of the hosting tasks you're responsible for.
If you're unsure of how to charge, one thing I don't recommend is pegging your pay to the amount billed to the guests. It wouldn't be fair for you to take a pay cut when the host offers a discount, when you're doing the same work.