this what CIC website says>
When you sponsor a spouse, common-law or conjugal partner, or dependent children to become permanent residents of Canada, you must promise to support them financially. Therefore, you have to meet certain income requirements. If you have previously sponsored relatives to come to Canada and they have later turned to the government for financial assistance, you may not be allowed to sponsor another person. Sponsorship is a big commitment, so you must take this obligation seriously.
here is the link http://www.cic.gc.ca/english/immigrate/sponsor/spouse-apply-who.asp
so - you have to meet "certain income requirements", which is different than "minimum income requirements". Certain categories have a minimum requirement defined by a number, and if you don't meet the minimum, you can not sponsor, full stop. Not much possibility for discussions/negociations.
For Spousal sponsorship, you have to prove that you have a plan on how you will support yourself and your family when they come to Canada, but there is no minimum - you have to demonstrate that you have thought about it, that you might have savings, or parents willing to sponsor you, or a house where you will live etc, but there is no number that you need to reach. You need to prove that you are not on welfare, and that your family will not go on welfare, but that's it.
on the sponsor guide it says:
In order to sponsor, you must...
be 18 years of age or older,
be a Canadian citizen, Registered Indian or permanent resident,
be sponsoring a member of the family Class,
live in Canada or provide evidence , if you are a Canadian citizen living outside of Canada, that you will live exclusively in Canada once the person you are sponsoring becomes a permanent resident.
sign an agreement with your spouse or common-law partner confirming that each of you understands your obligations and responsibilities,
sign an undertaking promising to provide for your spouse or common-law partner's basic requirements and, if applicable, those of his or her dependent children,
prove that you have sufficient income to provide basic requirements for your spouse or common-law partner's dependent children. To do this, you must provide documents showing your financial resources for the past 12 months. This requirement applies only when dependent children who have dependent children of their own are included on the application.
(link http://www.cic.gc.ca/english/information/applications/guides/3900ETOC.asp)
you can see on the last paragraph - you have to prove that you have a sufficient income only if you are sponsoring children - if you are only sponsoring your spouse, you don't have to. It's always best to include information on how you will support yourself so CIC is convinced that you will not go on welfare, but no minimum.
Cheers,
Sweden