How does one go about starting a line of food products?

Actually it can be both.

Depends on where you are in the supply chain. Do you want to cook/prepare the food? If so you need a commercial kitchen (where I live one can rent space in existing kitchen). I do not believe you can just do it from your home kitchen. At least not in New York. Next is distribution – online or offline. Offline is much more expensive for you since you will have to pay for all the logistics, whereas if you do it online, the buyer can (should) pay of the shipping (that is if the product you are planning can be stored and shipped. There are a host of other issues. I hope this gets you started.

Read The 4 Hour Workweek . The author did something similar with vitamin/supplents.

Create the recipes for your winning products.

Write a business plan that shows why your product will succeed in the market. That needs to include your competitive advantage, market research on the size of the market for your product, a list of your competitors (direct and indirect), a marketing plan (how will you sell—retail? Web? direct?) and where will you sell?

The you have to have the funds to create packaging, produce the intial products, and get them to market.

First, you can create the demand to begin with and proceed with the other aspects of the business later*, that is, presuming that you have some products you already make, start approaching local supermarkets, street fairs, etc., and do taste/sale offerings. fine tuning as you go along. The matra of this business model is ‘Ready-Fire-Aim’.

Second, listen to your clients!
Often (not always) their observations will point you in a direction you didn’t think about (as an analogy, if you saw ‘Sea Biscuit’, the movie, you’ll recall that the entrepeneurial character of Jeff Bridges opened up a shop to sell bicycles, yet when seeing his venture wasn’t panning out he took a new and eventually very successful course upon encountering the opportunity to serve the needs of a new emerging market, that of the automobile.

*do get the at least the appropriate sanitation/business licenses before you begin.