Sous Chef

Test market at a farmers market. You can create your own labels at home.

Patenting (as opposed to branding) a ketchup is pretty tricky as it is a generic term that has been around for centuries. Your formula would have to be extremely unique and it might take a century to protect your rights. Even if it's successful someone is going to reverse engineer it anyway. Most condiment startups begin with bottling in one's own home kitchen and selling door to door (think sriracha "Rooster" sauce). Once you can afford it then you can move on to buy or lease a facility that will do an assembly line bottling job which must be USDA inspected.

There are lots of graphic design programs for free on the web you can use to make your label.