It's not a good idea to take a wild animal into your house accept in very rare situations. Baby cottontail rabbits are very hard to keptkeep alive without their mother for a number of reasons. First, they have poor immune systems and the little immunity they do have comes from the mother's milk. Without that they often die. Also-you can not buy rabbit formula at a local pet store. RabbitsRabbits' formula is very different from human, dog or cat formula. Rabbits are vegetarians and don't digest those formulas well. Also, a mother rabbit usually only nurses her babies for about 5 minutes per day. Therefore each baby probably only gets about a minute to nurse in a 24 hour period. Therefore the mother rabbit's milk is extremely high in calories and fat. That is not the case with dog and cat formulas you will find at local pet stores.
Rehabilitation of a baby cottontail is very hard but it is not impossible. I actually found a baby cottontail when it'sits eyes were still closed. It was likely only 2-3 days old. It was layinglying alone on a hot sidewalk. It was probably dropped by a cat that removed it from it'sits nest. The nest could not be found and the rabbit looked close to death so I brought it inside. I knew nothing about baby rabbits at the time but I read all I could. I first hydrated the bunny with drops of pedialyte and an eye dropper. I then switched to puppy formula mixed with probiotics for rabbits. I kept the bunny in a covered aquarium with a heat lamp on one side. It's a very long story from there but that was two years ago and the cottontail is now a house pet. He eats rabbit food, hay and veggies like a domestic rabbit would. He lives inside my house in a huge 3 floor cage and is literlitter box trained! He's skittish and doesn't like to be picked up. However, he lets me pet him and he will eat out of my hands. I
I made the decision not to release him to the wild because I felt he probably would not survive. I live in the woods with Bobcatsbobcats, fishers, fox and coyotes. The rabbit hadhas learned to ring a bell when his food dish is empty. Obviously, that is not going to work well in the woods. He seems very happy. I'm sure he doesn't miss the wild since he has never experienced it.