Rowing has heavyweight and lightweight categories. And if you're very small, you can become a coxswain - the person who steers the boat and orders everyone around. Rowing offers age categories from high school to the ancient, handicapped so you race against people you own age. There are rowers still competing at the national level into their 90s. Young rowers are restricted mostly by the equipment, which is adult size.
Most kids start rowing when they are in high school.
Yes, in fact, because rowing is a sport that involves mostly legs, women do as well or better than men. And one of the fastest growing populations of rowers are women - high school, college and masters women. Rowing well requires a moderate to high level of fitness. Physical skill doesn't matter. We'll teach you how to row.