Because when you borrow money together, both people are joint and severally liable for the debt. That means, that the bank can sue both of you, or only one of you to recover the debt.
What if your friend loses his job and can't afford the repayments? You'll have to pay 100% of the debt even though you're only entitled to 50% of the income. Plus, when you go for a new loan next time, the new bank will assume you have 100% of the debt even though it is a joint borrowing.
Borrowing jointly is fine for married/de facto couples because that is part and parcel of the relationship. When it comes to friends/associates, do not do it unless you know them very well, and they are in a strong financial position.
What if your friend loses his job and can't afford the repayments? You'll have to pay 100% of the debt even though you're only entitled to 50% of the income. Plus, when you go for a new loan next time, the new bank will assume you have 100% of the debt even though it is a joint borrowing.
Borrowing jointly is fine for married/de facto couples because that is part and parcel of the relationship. When it comes to friends/associates, do not do it unless you know them very well, and they are in a strong financial position.