The reasons for the guest room’s popularity are the same behind its demise. You know the facts: Homeownership has been replaced by rental agreements, flatshares are more common than family units, and suburban homes have given way to (very) small city apartments. “Today, square footage is at such a premium, the idea of having a guest room feels like a luxury from the Gilded Age,” Sarah adds. When you get less space for your money, prioritization becomes key. It’s something design advisor and WeIncontro founder Helena Agustí knows all too well. Her unique eye for decoration has made the homes she’s lived in real Instagram candy. When she searched for…