Hello Jude,
I just started co-hosting for 3 rather big units (3 bedroom/3 bathrooms) in Malibu, CA. The units are right on the water and go for premium during the summer season (slightly lower in the winter). I do not clean the units myself but manage the cleaning crew schedule and supervise thier work, do not order supplies but manage the inventory, communicate with guests, greet them (when possible), arrange for repairs, etc. I get paid 7.5% of every listing minus Airbnb fee, not including the cleaning fee. To be honest, it's a lot of work, even when I don't need to come there, but hours are flexible (which is very improtant to me) and very close to my house, so I will have to see how it will progress. The fee is always negotiable with a host. I say if you just co-host just one unit, your % should be higher. Also, agree on a minimum pay for you with a host, before you start co-hosting. The nightly price might go down, especially during a slow season, your pay check might be considerably less (the amount of work will probably remain the same).
I hope my answer helped