To be a sponsor:
You and the sponsored relative must sign a sponsorship agreement that commits you to provide financial support for your relative if necessary. This agreement also states that the person becoming a permanent resident will make every effort to support themselves. Dependent children under age 22 do not have to sign this agreement. Quebec residents must sign an “undertaking” with the province of Quebec—a contract binding the sponsorship.
You must promise to
provide financial support for the relative and any other eligible relatives accompanying them for a period of three to ten years, depending on their age and relationship to you. This time period begins on the date they become a permanent resident.
From
http://www.cic.gc.ca/english/immigrate/sponsor/relatives-apply-who.asp