If your family member offers to pay for your vacation in exchange for a few nights of babysitting their children, you take them up on that offer. What's a day of watching your nieces and nephews if you get to live it up on vacay for the remainder of your time there? That's right. Absolutely nothing. When your family member's friends start asking for some free nannying, you draw the line. Last time you checked, they didn't pay for your vacation. Your family member did. It might get a little unco…