Rules for finances & family/friends:
1. I don't loan money, if I want to help them out, it's a gift, not a loan, regardless of size. I've gifted thousands before, no strings attached. If they want to repay me later, it's a gift, not a loan repayment. If there is no expectation of anything coming back, there are no hard feelings when it doesn't.
2. I don't cosign for anything, nor would I ask them to. They are family, if they are kicked out onto the street or starving for lack of food, I'll help them out, but I won't tie my finances to them in any way.
If the bank won't loan them money on their own credit, why would you?
I've seen relationships permanently ruined because somebody was "so kind" to a family member or friend by loaning them money or tying finances together. Best intentions don't matter.