If a person takes out a loan in my name but the debt is not mine, rather it is for him, is there any sin on me if he does not pay it off?.
What we understand from your question is that you want to take out a loan in your name, so that someone else may benefit from it, and this person may or may not pay it off. In that case you will be expected, according to sharee’ah, to pay off the loan because apparently you took it for yourself, and the loan was given on that basis.
If you know that the borrower will never pay it off, then you should not help him to get that loan, because by doing that he is a wrongdoer and aggressor who is exposing himself to the punishment mentioned in the words of the Prophet (peace and blessings of Allaah be upon him): “Whoever takes people’s wealth intending to pay it back, Allaah will enable him to pay it back, and whoever takes it intending to destroy it, Allaah will destroy him.” Narrated by al-Bukhaari (2387).
But if you intend to pay it off for him if he refuses to pay it off, then there is nothing wrong with that, and you will have done him a favour with this money.
To sum up: So long as the loan is in your name, then according to sharee’ah you are responsible for paying it off.
And Allaah knows best.