I'm obviously paraphrasing, but Ulysses S. Grant starts his autobiography off with something along the lines of...
"My friends have been suggesting for years that I write my memoirs, but I've always told them hell no. I hate writing, and I've got no interest in such a thing... and that's still true to this day. But I've become old and short on cash, and some people offered to pay me."
He's a President I always liked, and felt was underappreciated... But his memoirs paint a different picture than I expected (on personal style and stuff). I'm not far into it yet, though.
Imagining a former President who's short on cash in his retirement seems so alien to modern notions of POTUS pomp.