Hi there! Not sure where you're located in the world but hopefully this page from my website will help you with some things:
If you buy bulk for cake boards and ingredients and whatnot and you will save a ton of $$. You may be able to buy direct from a local distribution warehouse that carries bakery supplies. That sort of listing is harder to find through regular channels but if you call a nearby bakery and ask like a curious customer instead of potential competitor, they will probably tell you how/where they get their stuff. Around any major city, there is always at least one such place.
Hope this helps and good luck with your new cupcake biz!