well, the pickup line isn't without context. prostitution is illegal, but the definition of prostitution is very narrow, specifyied by directly receiving genital-genital intercourse through compensation (money). so there's a subculture of enjo-kousai (compensated dating) where girls accompany older men on dates (meals, movies, etc). since there's no express requirement for sex, it technically skids the definition of prostitution (although the males usually expect sex, natch).
i'd be pretty damn proud if my plumbing was still operational at 81, though going for a teenager at that age...