@Christine4594
Yes...absolutely. The owner just invites you to Co Host via email. When you receive the email and accept it, you're all set.
I would recommend you have a written contract with the owner that clearly spells out who does what and what the compensation is for you. Be sure to include what happens if things don't work out and the agreement will be terminated. I usually suggest a short initial contract (3months) so either party can go their separate ways if things don't work out.
What Can Co Hosts Do
https://www.airbnb.com/help/article/1534