German host families rely on their au pair to be committed and to stay with them for the entire length agreed on in the contract. In the event that the contract is being terminated earlier, the au pair will be responsible for paying her / his own return flight home which would otherwise have been paid for by the host family if you had previously agreed to stay with them for full 12 months. Furthermore, your visa will expire after termination of the program. (In case of a rematch with another host family, the visa will have to be changed over to the new family.)