This.
You should probably get one snake and see how it goes. If you just go dump money into a rack and 15 snakes to start you might quickly decide that you don't like to clean poop and change water for 15 snakes every day. Plus it's easier to learn this stuff and get husbandry down while you only have one snake. If husbandry is off on a bunch of animals and they all come down with respiratory infections your vet bill might put you in the poor house.