Not exactly sure what is in it, but why not enter and find out? (30 Days)

The Treasure Chest House changes the appearance of your Mini House. It also increases the number of shop slots available and the HP + SP regeneration you receive while resting. You can apply the new Mini House by pressing "H" and clicking "Change Outlook".

Shop Slots: +5
Duration: 30 days
Binding: Binds to Character
Usage: Unlimited