""Mi casa, su casa" is "my house is your house!" in Spanish.
Or if you add a question at the end - "Mi casa, su casa?" That could be the Spanish equivilant of "your house or mine?"
Of course that does not really matter here as we are talking about a CASHA - my Spanish for cache.
You know what to do, right! - Bring a pen and watch out for hungry hippos (I mean muggles)!