"Sometimes, I just wish that I had a chance with him, you know? Like, even if I had to become a girl, I’d do it." (Or the one where Kellin takes a drug that turns him into a woman.) Also, this is rated for later chapters.
Looking after a sick mother, working as a waiter for minimum wage and watching your little sister do prostitution is something Kellin doesn't want to do for the rest of his life. So when an opportunity comes to change his life for the better, he'll take it. Even if it does mean marrying a stranger.