1. You need the support of your ISP, because they will need to 'Lease' you IP's for your connection for each of your servers and you need to be able to order them as you need from your ISP without any hassle.
2. You need to custom build some good boxes (servers) with come good processors and good stable hardware in them.
3. You need to keep a cache of parts on side, such as memory, hard drives, NICs, etc, in case your clients have issues or need upgrades.
4. You need to keep pre-configured spare routers / switches on-site, just in case one of your switches or routers fail, you can quickly swap it out.
5. You will need support staff to work around the clock monitoring servers and also monitoring for reboot requests, etc.
6. You will need a few thousand dollars to start with, even if it's just starting your own VERY small 5-10 server data center from your home / home-office. This is how MOST start and as your business grows, move your location to a store front / office building or buy a large storage shed or something that is weatherproof and protected from elements of the Earth.
I hope this helps give you some insight. Good luck! If you need support staff, give me a shout!