I don’t know much at all about webhosting apart from the fack I pay my hosts a certain amount and my sites are online.

How would you go about starting your own hosting company, what would you need to buy?

you would need to get either a reseller account, a VPS, or a dedicated server.

I definitely recommend starting off with a Reseller account. That way it gives you a feel for the business, and you dont have to worry about things like hackers, learning a new operating system, and arnt responsible for the hardware (not to mention the initial investment)