I want to try to volunteer with Workaway, but I want know first whether I or the host will pay for the plane ticket. Because if I need to pay, maybe I can’t afford it.
You haven't done much research...
The Information for Workawayers page states:
Remember though, Workaway.info is not an agency. We enable you to find placements. It is up to you to write yourself a great profile, to make contact, to introduce yourselves with an e-mail, to organize your travel arrangements, to arrange your travel visas, and to discuss directly with your host the ways in which you can volunteer , work or help.