For sale: Slightly used sister

Have a character write an ad to sell his or her sister.

Usually the dynamic is the annoying younger sister. What if it's an older sister? Teen? The perfectionist? The favored one? The one with super powers? The "different" one?

It could be an adult character writing it as a joke. Or not a joke.

What if the sister saw it? What ad would she write in response?

What if someone responds?