Hi, here are some things I discovered about retail that confused me at first-
Lice Cold Retail Freezer:
-You can sell fruit, veggies, and herbs through the freezer, but NOT fish or flowers. If you want to sell fish or flowers they have to be individually displayed and marked for sale.
-Items placed in the freezer will be marked for sale automatically.
-Sims will also buy herbal remedies (OR) from the freezer
-Mixology drinks and drinks from the espresso bar (GT) can be placed in the fridge, but sims actually won't purchase them and occasionally may drink them for free. *Edit- Actually, this is wrong. Sims will buy drinks from the fridge, but not ones that were already drunken from.
Warming Rack:
-Only "warm" items may be stored here. When full it will look like there are birthday cakes inside, but those cakes can't actually be stored in the warming rack.
-Sims will occasionally steal a serving from anything stored in the warming rack.
Refrigerated Displays:
-Some cakes (like Birthday cakes [cooking skill], tiered cakes [gourmet cooking skill], carrot cake [baking skill]) can only be placed on the three spots in the upper-right portion of the display case. As in, the middle and right spots on the top row, and the right spot in the middle row. Other items, like the SimCity Cheesecake and the Gourmet Fruitcake, can be placed anywhere.
-After an item is sold from a display case, the sign has to be removed by your sim, but signs that are on the ground or on shelves can be deleted through the inventory (sold for $0), which might save some time. (Signs in planter bowls also have to be removed by a sim)
Misc:
-Plants that are marked for sale will automatically be un-marked for sale when they're ready to be harvested.
-You can't water, weed, or otherwise tend to plants that are marked for sale.
-"Normal" quality mushroom plants sell for ZERO simoleons. So, don't even bother. *Edit - Other items that also sell for $0: poison fireleaf plant, simcity cheesecake, and walleye surprise. I wonder if this is a bug.
-Herbal remedies (OR) are surprisingly profitable, especially the mid-level ones that don't require a lot of rare ingredients; like Energizer Infusion, Clear Mind Distillation, even Tummy Therapy. I'd recommend at least a 50%+ markup though.
-Sims won't buy drinks from you if you use the "tend" interaction on the mixology bar or the espresso bar (GT).
There are still some things I don't know, like whether or not you can sell upgraded appliances (and if so, will they be worth more?), or whether or not you can sell tea, base-game coffee, and quick drinks like orange juice and milk. But I hope this will be helpful to some people who might be confused about how some of the items work. And if you have any other tips or if something I wrote is inccorrect, please let me know!