Sponsorship - Not to be entered into lightly.
As a sponsor, you undertake to provide all basic requirements to the sponsored person: food, clothing, shelter, fuel, utilities, household supplies, personal requirements, and other goods and services including dental care, eye care and other health needs not provided by public health care.
You undertake that the sponsored person will not have to apply for social assistance.
For a spouse, the period of undertaking begins the day on which the sponsored person enters Canada with a temporary resident permit, or if already in Canada, on the day on which the sponsored person obtains a temporary resident permit following an application to remain in canada as a Permanent Resident, and in any other case on the day on which the sponsored person becomes a permanent resident (I assume that is date of landing).
The undertaking remains in effect no matter what happens in your life such as divorce, job change, unemployment, returning to school, etc. It is unconditional and cannot be terminated. If the sponsor does not provide the promised support, the sponsored person can take legal action against the sponsor.
If you default, and the sponsored person goes on social assistance, the sponsor is required to repay the government. This becomes a debt and the goverment can pursue the debt under the normal collection process including wage garnishment. However, the government may choose not to take action against the sponsor if the default is the result of abuse or in other circumstances. They reserve the right to take action against you at a later date to collect on the sums owed.
The sponsored person also agrees that they will "make every reasonable effort to provide for their own basic requirements", but that is it. There are no other obligations placed on the sponsored person.
Unless entered into jointly, the sponsor is not responsible for any debts incurred by the sponsored person to any party except the government.
And finally, you cannot enter Canada on a sponsorship that has been obtained on a fraudulent basis. If you can prove that the person entered into a fradulent relationship with you solely for the purpose of entering Canada, you may have a case for their deportation.