There's a trick to starting a new business: find something no one else is doing, and do it well. Just having a unique product isn't enough (or even necessary). You need a unique angle. I noticed there's need for a particular kind of business in the hobby. I have no room to do this myself, but I thought I'd put it out there in case someone else wants to give it a shot.
The idea is simple: produce high quality livestock for complete newbies with cheap shipping. Just focus on the dozen easiest plants and inverts and have them all in one place. People who are just getting into planted tanks want easy plants, but they would prefer to buy everything from one seller and pay for shipping only once. Most sellers, including pet stores, will have some of these species. I haven't encountered any that have all of them for reasonable shipping.
For instance, there are about a dozen plants that are always recommended to beginners: java moss, java fern (regular, needle, trident, and windelov), anubias (nana and petite), water sprite, water wisteria, Egeria densa, hornwort, guppy grass, frogbit, duckweed/Salvinia minima, banana plant, vallisneria/dwarf sag, and Cryptocoryne wendtii (green and bronze). Even with the different varieties, you would have less than twenty species to keep track of, yet you would cover 90% of what beginners look for.
There are about a half dozen breedable inverts that are recommended to beginners: mystery snails (ivory, gold, blue, and magenta), trumpet snails, ghost shrimp, cherry shrimp (red, yellow, and blue) and ramshorn snails (red, pink, and blue; with or without leopard spots). Total varieties: 12.
You could also offer basic drystock, like gelcap root tabs, Indian almond leaves, forcepts, mini measuring spoons, and dry ferts in small portions. Beginners want these, but can rarely find them all in one place. Don't try to offer more than the bare essentials, though - you don't want piles of stuff in your house.
Most people buy fish locally, but if you wanted you could offer some higher quality strains of the easiest species: bristlenose plecos, guppies, platies, swordtails, danios, cories, longfin whiteclouds, etc. Or just some easy rare fish: Heterandria formosa, gardneri/australis killifish, endlers (black bar, tiger, chili), etc. It probably would be best to focus on plants and inverts, though, since they don't have as much bioload and aren't as hard to ship.
The shipping would be the main selling point: Everything you need, with a live arrival guarantee, for a set shipping price (no added charges for heat or cold packs). Priority shipping would be ideal.
Keep it easy for yourself to keep it easy for the buyer: don't tinker with the water, don't use special foods, standardize the shipping process, and have set prices for everything. Ideally, you would grow the plants submerged, but emersed would be fine for most of them.
Set up your tanks to hold one or two species from each category. For instance:
Tank 1: Java moss, floating water sprite; blue ramshorn snails, blue mystery snails, blue cherry shrimp, black bar endlers(?).
Tank 2: Frogbit, Egeria densa; red ramshorn snails, magenta mystery snails, red cherry shrimp; longfin cories(?).
Tank 3: Guppy grass, Salvinia minima; pink ramshorn snails, gold mystery snails, yellow shrimp; Heterandria formosa(?).
And so on.
If anyone wants to set up a profitable fishroom, I think you could make a lot of money by catering to newbies.