A second person on the mortgage who shares the responsibility for paying it back. Their credit and income are also evaluated. Usually a spouse, partner, or family member.
A co-borrower is someone who applies for the mortgage with you and becomes equally responsible for paying it back. Most often it's a spouse or partner, but it can also be a parent, sibling, or even a friend.
The lender evaluates both borrowers together: combined income (which can help you qualify for more), combined debts, and both credit scores (lenders use the lower of the two middle scores). Both names go on the loan and the deed. Both have to sign at closing. Both can be held responsible for the full balance if payments stop.
This is different from a co-signer, who's responsible for the loan but typically not on the title and not living in the home.
Example
You earn $60,000 with a 720 credit score; your spouse earns $50,000 with a 760 score. Together you qualify based on $110,000 income, but the lender uses 720 (your lower middle score) to price the rate.
Also known as
joint borrower, co-applicant, additional borrower