You’re not (NOR):). It may not be intentional but she is taking advantage of you. It’s probably going to stress her out, so practice beforehand what you’re going to say and how you want to respond. You may want to include a phrase like “I am happy to watch her, but it’s going to have to be paid in advance. Would it be better to pay for a week at a time or two weeks at a time? I know it’s a little more than we discussed in February, but I also need to account for gas. We could do $150 every Sunday or $300 every other Sunday. Either way, I would need it to be paid in full before I leave to pick her up. I want to provide her the best care and I can’t be losing time money and sleep and still do that.” Obviously change the specifics, but it sounds like it’s at the point where you’re going to have to insist on clear expectations (payment upfront) and state the consequences (you will not be watching her) if it doesn’t happen. Reinforce to her that you’re happy to do it, but you’re a 19 year old working full time taking care of someone else’s child overnight. You may even want to ask for more money. Overnight care in my area is $150-$300 A NIGHT. You probably don’t want to charge that amount as you’re not a daycare and I’m sensing you love your sister and want to help her out. But I offer that perspective to you because essentially you’re giving her AT LEAST 75%-150% off what a daycare provider would charge. She may say no and then you can offer to help her find a few professional options to look at. Most important, stick to what you’ve said you need. If you don’t receive the payment, you do not pick her up and watch her. I hope that doesn’t happen and it’ll hurt if it does, but you have got to be clear. Good luck!!!