4 is the minimum I would start with. If you're new, tractor supply, but there are people who ship them like cackle and McMurray that are reliable. Just watch a video on youtube. They just need food water and shelter like you. Only thing extra is nesting boxes and dust bath, which is really just sand or dirt mixing in some diatomaceous earth is helpful. Design for the winter tho.

If you're just getting started and want to skip the brooder/chick stage and get eggs faster look for chickens already laying eggs for sale in craigslist and in local livestock exchange groups on FB. Lay production starts to really drop after 2 years old so age is something to consider when going this route.