It could *definitely* affect your retirement plans. If you co-sign, you are legally obligating yourself to pay if  you son does not. If you son defaults on his rent--or otherwise breaches his lease--the landlord can proceed against you for the money. You will then either have to pay the amount owing--i.e. spend your own money, which you may or may not be able to afford--or if you don't, then you will be default, too. If you default on your obligations, or are sued on them and lose, so there is a judgment against you--then that will show on your credit report and negatively impact your credit score, and thus you ability to borrow and the terms under which you could borrow. Co-signing for someone else is rarely a good idea--you get the downside of the fiscal obligation without much upside. It may be better if your son looks at other options--e.g. taking roommates to help pay for the premises.