Contracts are very standard and it is possible that for some smaller schools the contract may only be given on your arrival in to resort. Other ski schools will expect a signed contract up to 3 months before arrival and will be subject to you successfully completing the SIA course and instructor exams.
You will normally be allocated accommodation and a lift pass together with ski school uniform. The contract will explain the payment system and the working hours of a normal week. It will detail your start date and will ask if you are available to work till the end of the season or if you must leave on a certain date. It may be that you are required to pay a deposit for the uniform and/or the accommodation, which is returnable at the end of the season. You must be available for work during peak season times. This is Christmas and New Year, most of February and Easter (if the resort is still open). Do not request time off during these periods!