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Greetings @Brandi123 and welcome to BYC! There's a wealth of info regarding all you'll need to know over in the learning center of the site and throughout the various threads. Get comfy and browse around !
A chicken tractor isn't really designed as a "sole source feeder" but more as a "container" and fresh vegetation/bug supplement machine. You'd need a pretty big tractor and small number of chickens to be able to have them survive and thrive/grow adequately (think enclosed free ranging). Inside the tractor, you'd need to feed and water them daily whether you were moving the tractor around or not. If you wanted them to have access to fresh grass/weeds and bugs, then you'd need to move the tractor, depending on numbers of birds inside, possibly multiple times a day. If you leave the tractor in one place it would be adequate as basic housing, but they'd strip the ground inside to bare dirt (think surface of the moon bare) in a matter of hours or days depending on the number of birds contained within.
If you're going to buy chicks, you can feed them a basic chick food from the local farm store. I believe even many walmarts now carry small bags of various chicken feeds. You'll need to keep them on the chick food for several months or until such time as they have access to grit. Chick feed contains the grit they need to digest the food. The other thing is you'll need to provide chicks access to warmth via some sort of heating device for their first few weeks of life. This can be a heat lamp or heating pad etc. You need to give them adequate space to get away from the heat source also so they don't over heat. They'll typically need this until they are fully fledged (have all their feathers grown out). Many keep the chicks inside in some sort of containment area (box/bin/bathtub/etc) for the first few weeks, but do keep in mind they are going to poop and it will build up a stink, and they are going to create a LOT of dust/dander. Also, believe it or not, they WILL be able to fly up a foot or more by the end of their 2nd to 3rd week, so keeping them contained may require some sort of cover.
Good luck and keep us posted on your progress! Pictures are always appreciated!