The paid one will be differ, you will buy a high space reseller hosting account and through this account you can sell small plans with your own prices. For free reseller hosting, I'd recommend Resellers Panel where you can get a fast account for free and you can get your own domain that you can host your hosting business in it.
For paid reseller hosting, I'd recommend Host Gator as you can easily build your own unlimited domain hosting business in minutes. For only $24.95/month, you can get a very good hosting reseller account where you can sell small hosting plans and keep the whole profits.
After you choose your best reseller hosting option, you can promote your business using some methods. The first and the most effective one is the Pay per Click advertising. Programs like Google Adwords will be very good for your business as it can bring you targeted traffic, this traffic will be more than willing to buy your services.
The second good method is to write articles about web hosting and submit them to free article directories like Ezine Articles, Hub Pages, Squidoo and other similar websites. You will get targeted traffic to your website and in the same time you will get some good that help you in search engines.
You can also create a free blog at Blogger.com; you can also promote your business buy joining web hosting forums where you can add your link at your signature area.