When adding someone to your mortgage, pull all of the credit reports copies for both signers on the new mortgage loan. Look at your co-borrower's credit carefully. If you have excellent but your prospective co-borrower has poor credit, then you will end up with a less favourable loan once you refinance. Calculate the DIR (debt-to-income ratio) with the co-borrower's income added. Look for mortgage lenders that are based on your FICO scores, apply to two or three lenders only as too many applications affect your FICO scores negatively, and then choose an offer after reviewing all of them, and complete the loan process.