Is it permissible for a 21-year-old girl to tutor a 13-year-old boy alone in a house, knowing that the girl needs money for her marriage?

It is not permissible for a girl to be alone with a boy or to uncover her body in front of him if he is an adult or a teenager nearing puberty. The ruling for a teenager is the same as for an adult regarding the necessity of veiling from him. Moreover, a girl's need for money does not justify her seeking sustenance through disobeying Allah. She must fear Allah and seek sustenance through lawful means. She can teach females instead of males.