I see that you're in Madrid but you didn't specify in your subject title or the body of your posting. So we should assume you intend to give these English classes at home in Madrid, correct?

The sister/brother-in-law of my ladyfriend, whom all live in Madrid, recently hired an English woman to come to the sister's house to be a kind of English tutor. The boy's only 4 years old so it wouldn't be teacher/student relationship but rather a play-relationship where they would only speak Spanish.

I would think there would be SOME market for this kind of thing for you. How much would you charge? Have you ever done this kind of thing before? Good luck!

Saludos, MadridMan