If you're raising snails to sell to restaurants, caterers, gourmet food stores or private clients, you're involved in an ancient tradition. Technically known as heliciculture, keeping snails for food dates back to the Roman Empire, if not earlier. Raising escargot for profit doesn't involve a lot in upfront capital, but it does require a lot of physical, often unpleasant work. It's no get-rich-quick scheme, but it can provide additional income for small farmers or those interested in producing local table fare.
Escargotière is the French word for snail farm. The type of snails most often raised for the escargot market are Helix pomatia or Helix aspersa. Depending on where you live, the latter might already inhabit your garden, munching away on veggies and leaves. Capture a few dozen of these snails and you'll have plenty of potential escargot in short order. Snails reproduce so rapidly they make rabbits look like amateurs. Snails are simple creatures, and eating and reproducing make up the bulk of their activities.
Before starting your snail-raising venture, check your state regulations regarding snail farming. If you're planning to raise a non-indigenous species, you'll need to meet U.S. Department of Agriculture containment guidelines, which are extremely strict. No matter what type of snail species you raise, you might receive a visit from a state inspector to check out your facility. You'll need a USDA plant pest permit to move snails across state lines, whether importing them to raise or shipping them live to customers. You can't import live snails into the United States for human consumption.
Ideally, you can raise your snails outdoors in pastures planted specifically with snail nutrition in mind. If that's not practical, you can raise them in pens, with solid fencing designed to keep snails in and predators out. Since birds like the taste of snails, cover the pens with netting to keep them out. If you're squeezed for space, you can raise snails in plastic or wire baskets, but these enclosures require regular cleaning. Don't overcrowd your snails; this can cause a die-off. Provide them with lettuce and other nutritious, leafy vegetables. Before sending your snails to market, you must purge them of grit and other undesirable intestinal detritus. If you stop feeding them several days before marketing or cooking them, that will usually do the trick.
While you may market your snails directly to local restaurants and similar establishments seeking escargot, it's possible that businesses requiring a steady source of quality snails will pay you to grow a suitable product, even providing you with snail food and breeding stock. For example, a local restaurant might have leftover produce no longer suitable for serving to customers but perfect food for growing top snails. You can also sell your snails through companies providing chefs with specialty foods.