they didn't sell furniture

In one episode Julia said that they only sold "nick-knacks." Not furniture. I guess that would include lamps and such. No problem for one delivery man. I would hazard the guess the larger furniture was ordered elsewhere and they delivered it.

The selling of furniture

Many times throughout the run of the show it was said that the Designing women did sell furniture. For just one example in the first season I am not sure of the name of the episode the women land themselves in jail for buying a warehouse of stolen furniture and goods from a friend of Charlene's because they were low of money.The man said he was an importer and since she was such a good friend he would give them a deal.

taking inventory

There have been many times throughout the series when there have been examples of the Sugarbaker Firm selling furniture.In the episode where they hire Anthony's girlfriend Vanessa to do inventory she has trouble with knowing the difference between a settee and a sofa.Also later in the series when Allison and Carlene come along they along with Anthony get locked in the store room over a weekend and the storeroom is full of furniture.It is very possible that they order a lot of their things but it would make sense to me that they would want to check them out before they are delievered.