My sister wants to borrow $800 to get her car repaired. She is terrible with money and doesn't bother to change her poor habits, so I'm on the fence about loaning her the money. My sister needs her car to get to work, which I understand. I'll likely fund the repair. When I give her the $800 how do I best make her understand that it is a loan and not a gift? What is a reasonable amount of time to expect her to pay me back. She makes $14 an hour, has a lot of debt, but very few bills. She only pays a car payment and insurance. To be clear, I can't just gift her the money - $800 is a large sum to me and we have huge student loans to pay off.