Co-signing a note means that you are signing for another person and stating that if for any reason they default on the loan you will be responsible for the payments, your credit will also be affected in the event of late payments or foreclosure as well as the borrower’s credit. Since you are jointly responsible for the mortgage payment this may affect your ability to qualify for new loans in the future because your credit report will also reflect this as a mortgage and will be included in your debt to income ratio when qualifying for a new home purchase.