Actually I had this problem before as well. Had the basic apartment and my crafter created a fir shelf that said it could hold craftable home items or something of the such. Excuse me if I can not tell you the name of the shelf or the actual message, I am at work. Every time I tried to place it said had to upgrade my house. Just kept it on my alt until my main recently upgraded to a 3 room house and started placing items through the house.
What it does is allow you to place it in one of your home broker slots and store crafted items your carpenter would like to sell. The one I have holds like 50+- items. Not sure if I placed it in the house 1st then on the broker slot or placed it in the broker slot then somewhere in my house. Has been a little while. Since I have 3 broker slots 2 of them have a 32 item chest and the other is the shelf. Do not sell much off of it yet seeing that most items level 30 and below sell for less then a gold unless rare, then most often can make more from the rare then the crafted item.
Hope that helps