For a full private sponsorship covering twelve months, the published figures are $21,400 for one person, $29,900 for two, $34,100 for four, and $38,100 for six, with roughly $3,000 for each additional person. Blended visa office-referred sponsorships are about half that, because the government funds six of the twelve months.
Three warnings matter more than the numbers. The published table is a national average used at application stage only, and your real liability is set by local rates where the family will settle, so it can be higher. Borrowed money is not accepted, whether from a line of credit, a loan or a second mortgage. And linked applications are costed separately rather than combined.
The money is also only half the commitment. You are agreeing to twelve months of practical support: finding housing, enrolling children in school, health cards, banking, language classes, and simply being available.