For how to start, I would recommend starting with a reseller plan , unless you plan on having everyone sign up for their own hosting account, you will need a reseller plan as you can not "resell" space on a shared/basic hosting plan.
Then you will of course need your own domain name to promote and for users to signup on.
Later on, after you get enough users paying you, you can get your dedicated hosting, and either move the users you have as clients onto the dedicated or keep them on the reseller plan, and only move new users onto the dedicated hosting.
You can find information on Lunarpages reseller plan at :
http://www.lunarpages.com/reseller-hosting/The reseller plan is the best place to start, as once you start getting more users signed up, your cost for the "client accounts" will go lower, resulting in you being able to lower your prices as you go on.
One thing to keep in mind, if you are going to be reselling hosting, you will need to make sure you get a support system in place as soon as possible, as if users have any issues, they will want support, and they will want it as fast as possible.
I recommend once you start, you get at least 2 other people involved in your end, so each of you can take 8 hour shifts to provide 24/7 support to your users.