You need lots of things to start.
Firstly you need to buy a server. One dededicated server would be goood for a fist time. Where to buy ? This strongly depends on your customer location. I use http://www.servepath.com
with "busines path" plan. They run Secondary DNS for my domains and their support is fast enough.
Next thing you need is an account on payment processor. I can recomend http://worldpay.com
(great, but expensive) and http://2checkout.com
Then you need your own web site. This is very important part of your business.
You can find design you like at http://templatemosters.com
. Good site engine you can get from http://astellar.com
A couple of days to customize web-site and you are ready to sell hosting service ;-)