Is the host family responsible for the flight and visa arrangement or is it the au pair?

The visa application is for sure a joint effort: Depending on the host country, you will need to get the contract and the health insurance from the family. All the rest is up to you (scheduling an appointment at the ambassy and having your passport, picture, motivation letter,... ready)

Who organizes and pays for the flight is an agreement between you and the host family. See also these community discussions around this topic:

• https://connectaupair.world/community/question/can-the-host-family-pay-for-all-my-travel-expenses
• https://connectaupair.world/community/question/do-host-families-usually-pay-for-au-pair-plane-tickets
• https://connectaupair.world/community/question/would-i-have-to-pay-for-my-flights-to-and-from-the-host-country

Thank you!