You conjure a magnificent mansion -- a real mansion, not a half-sized hovel like some spellcaster who shall remain nameless.  It has a single entrance, which appears as large door finely crafted of rare wood.  When open, anyone can see inside to the splendorous abode.  When closed, the door is visible only to one who holds the key or a written invitation.   It exists in an extradimensional space, accessible only to you and those whom you explicitly invite by name.  It lasts for the duration, at which point it *poofs* out of existence and dumps anyone (and anything on their person) out on the street from whence they came.  Anything remaining in the residence is lost, presumably taken by some kleptomaniacal extradimensional horror.

The layout of the residence is solely at the discretion of the caster, and may consist of up to 15,000 square feet.  It must be bordered on all sides by stone or another solid material, as gazing into the abyss risks attracting the attention of aforementioned extradimensional horrors.  However, an open courtyard completely contained within the walls is perfectly acceptable. It may consist of multiple floors, and can even have a basement, although I don't know why you'd bother.  The décor and landscaping is similarly instantiated when the spell is cast.  The temperature is exactly how the caster wants it, and no amount of fiddling with the thermostat can change that.  By default it smells of freshly baked cookies, but that can be changed at will.

 While inside, the caster and any guest may cast Unseen Servant at will, although no one may have more than one servant at a time.   The larders and iceboxes contain sufficient food for 20 people, and an Unseen Servant may be ordered to prepare a gourmet meal to exacting specifications so long as it doesn't contain cilantro.

Nothing created as part of this spell -- structural, nutritional, or otherwise -- can exist outside of the residence, and deliquesce into a noxious goop should it be removed.