I'm purchasing my first house next month and wanna start a garden this summer my question is do I need a liscence to sell jars of homemade horseradish?

No

Horseradish will spread and spread once planted. Good stuff out of garden.

Pretty sure no in NY. Check with NY Agri Markets. Of course if your Amish your exempt. lol

https://agriculture.ny.gov/food-safety/home-processing

Should tell you what you need to know.

Be careful with the labeling. I met a guy who had all his products confiscated and who was fined, for not having both English and Metric measurements of the ingredients on his jars.

You can often buy the ingredients at produce auctions cheaper than you grow them, for most jams, jellies, pickles and sauces. You can also buy cheap produce to resell. One of the auctions I go to has lots of people at it, who make their living that way. One guy I know resells produce at 4 different farmers markets, that he buys at auction.

Keith

If you go to produce auctions, remember the lots are huge quantities. At least that's how it is here in Virginia. I agree with Keith C but sometimes the first timers don't know what they are getting into.