Some mortgage programs allow combining a spouse's income to increase borrowing capacity, but this often means both parties become liable to varying degrees depending on the contract.
Key points
Ask clearly: Who is the borrower?
Who is the co-owner?
Is each party responsible for the entire debt or a percentage?
Combining income can increase capacity, but it's a legal and financial decision, not simply adding a salary.
The figures, fees and limits in this answer vary by bank and change over time — confirm them with your bank or the official source before acting.