I have a year old labrador pup. The first 6 months were a total nightmare, no matter what they ruin a lot of stuff as well as messing the carpet.
Bear in mind a collie needs tonnes of exercise as it's a working dog. Be prepared to take it at least two, hour long walk a day.
They aren't a fortune to keep, my dog gets a £25 bag of dry dog food and that lasts a couple of weeks. Although, insurance is £16 a month. Dont risk the insurance, my dog was stung by a bee in the summer and it triggered an auto-immune disease that's cost me (luckily claiming back on the insurance) £2,000 to treat so far.
They are a lot of hassle and I'd recommend getting an older dog to start with, a rehome or what not, to get some experienxe before you take on a young dog.