Hey @Elizabeth3396 - welcome to the wonderful world of co-hosting! I personally have begun charging 15% but I have a range of 10-20%, depending on the level of service I'm providing (10% for just managing messaging and reservations vs 20% for setting up airbnb from scratch and managing all aspects of the business). The percentage you charge is also dependent on the area - so I would check to see what other co-hosts in your area are charging.
Also, I setup an initial pricing template and contract that I use with my co-hosts (just onboarded my first client using this and he AGREED!). Happy to share here and with our community in case anyone finds it helpful! I've also had a real estate attorney review it, so take it as my free gift to you : )
https://docs.google.com/document/d/1mgEF_LZU50U6l8hVHUuh5T8DRU0y5ZE4aC0rZvWE_D8/edit?usp=sharing