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According to the bilateraux laws with the European common market, aupairs from the European Economic Union are eligible for aupair visas in Switzerland for a maximum of 18 months. Aupairs must be between the ages of 18 and 25 years.
Relevant documents that the family may need can be found here.
You can work as an au pair in Switzerland for a maximum of 18 months. You will receive room and board with a host family in exchange for approximately 25 to 30 hours of weekly work (housework, baby-sitting, etc.). You have the right to one day off per week (at least one Sunday a month) and 4 weeks' vacation per year (5 weeks if you are less than 20 years old). You will be paid between 400 and 700 CHF per month depending on the age, experience and hours of work. Your employer is also required to enroll you in a language school, and will cover 50% of these expenses. The insurance is assumed paid by the au-pair, as her EU insurances will be valid in CH as well, however an accident insurance will be payable by the employer. No additional health insurance will be paid by the employer. Employee's share of social costs "AVS" can be deducted from the salary. This amounts to 7% of the salary (including the payment in nature, so room and board accounted at about 30 sfr per diem), so a total salary of about 1400 sfr. /month, for a cost to the EE of about 100 SFR. (although, many families will bear this cost, but it isn't an obligation). There is a legal obligation of adjusting the au pair time schedules so that she can participate in language courses, however there is no definition in the comparticipation to the costs.
Permits for au pairs from abroad are issued subject to quota regulations. Limits are placed on the numbers of individuals from specific countries who may come to Switzerland.
Further details for non-EU citizens regarding AuPair, Salary and general conditions may be found here.