"A hosting company" is a vague thing to want to setup, at the low-end you can have a single rack with random boxes in it. But to scale you need to consider run

"A hosting company" is a vague thing to want to setup, at the low-end you can have a single rack with random boxes in it. But to scale you need to consider running an AS, peering, redundant feeds, PSUs, having remote access to reimage machines, etc, etc. So rather than saying you want to be a host you'd get better response0s if you said what kind of hosting person you want to be? Random wordpress? Giving remote root on virtual machines? (Whats your antispam policy? How will you monitor incoming/outgoing bandwidth? What kind of routers will you use? What network topology to increase uptime? How many geographical locations?) Lots of people started hosting companies back in the day by filling racks with servers, before power costs made it hard, and these days reselling AWS, etc, is the simplest way to start - no need to worry about infrastructure, and still reasonably reliable.