For sous-vide you need three things:

1) A constant temperture water bath. This can be as simple as a pot of water in your oven or as nice as a shiny new $1000 digitally controlled thermal bath like the ones from Cuisine Technologies. A good compromise is a used or refurbished thermal bath found on eBay. They run $100-$300. Make sure you have room for whatever you get and that it can be placed near a sink for easy filling and eventual emptying.

2) A vacuum-sealer. Consumer models from FoodSaver are available for under $200. You really need the FoodSaver Pro model for about $199 (it is really still a consumer version despite the name) to have the flexibility to control the sealing and vacuum. Real “pro” vacuum sealers allow you to apply much larger vacuums but can cost over $1,000.

3) An accurate thermometer and probes. Ideally it should read within 1 degree. You’ll also want a probe–preferably thin–to stick through the bag and into your food. If you don’t also have a digital temperature control on your water bath you’ll want to get a probe for it that you can use to measure water temperature. Cooper-Atkins makes one for chefs that you can buy for under $100 from suppliers like eTundra.com. Compatible “K-type” probes are another $50 or so each. Some probes also require an extension wire for convenient use.

You can get started of course without all this. Place some eggs or a vacuum-sealed product from the store in a pan of water in your oven and monitor the oven temperature with a $3 oven thermometer and the internal temperature with your current meat thermometer and you’ll get some sense of what is possible, but for better results you’ll need to start investing!–David