Quotes from the guides:
Guide 3900
"Who may use this application?
This application guide is designed for Canadian citizens and permanent residents of Canada who are 18 years of age or older and wish to sponsor members of the family class."
Guide 3999
"Who may use this application
The enclosed instructions and forms are sent to the principal applicant (you) by the sponsor (a Canadian citizen or permanent resident) who wishes to support the application for immigration to Canada of a person (you) as a member of the family class.
The sponsor agrees to sign a contract (the sponsorship undertaking) by which he or she promises to provide, for a specific number of years, coverage of your basic requirements and those of your dependants, such as:
food
clothing
utilities
personal requirements
shelter
fuel
household supplies
dental care
eye care, and
other health care not provided by public health
It is important that you familiarize yourself with the contents of this guide before you complete the forms and return them to your sponsor. Your sponsor cannot submit the sponsorship forms until he or she receives your application."