I started babysitting for one family when I was 11 or barely 12. It was much too young. They had 4 kids and the very first time I sat, the kids had 3 friends over and the parents didn't warn me.
I hadn't changed a diaper before except on my baby sister, who was very patient. I got the youngest boy's very messy diaper off after much wriggling, and he suddenly made a run for it. It took me probably 30 minutes of chasing this kid around to pin him down long enough to get a diaper on him, largely because every time I made a grab for him, he hit me and squirmed away, and I was really, really not interested in grabbing him tightly enough to get poo on myself. Eventually, I got him sufficiently pinned down when he took a break in the carseat that was sitting in a hallway. Within 2 minutes of finally getting that diaper on, the parents got home.
That, friends, is why I had to apologize to the parents. "I'm really sorry, but there's ... stuff all over the carseat. And the hall floor. And the changing pad. I can clean it up if you give me a minute." I nearly broke down in tears, I was so mortified.
They didn't make me clean it up, but they were the worst payers in the history of babysitting (circa 1997, I got $5 for an evening with 7 kids). I watched their kids for the next several years. My parents made me keep doing it because they were friends with the family, until one day when the eldest son and I were both in high school and he and his friend spent the night practicing their pickup lines on me.
"Eddie is too old for a babysitter," I finally declared. The family disagreed, because Eddie refused to care for his siblings, but they got someone even younger than him to do it from then on.