Pretty sure it's all random and depends on a villager wanting to sell their furniture. Re-tail is based on whenever someone wants to sell rather than getting new stock like a normal store.
Just to refute the two posts above, none of my villagers have ever had sloppy furniture in their houses, yet I've picked up two from Re-Tail. In a year of playing, mind you.
Yes it`s random, and my peppy villager put sloppy and cardboard furniture up for sale in retail, and she never had them in her house, so it is possible but rare.