I am afraid if you want to start in hosting properly, you are going to have to spend some $$$ or your never even compete with the small hosts ,let alone the big hosts, We are talking Minimum of $200 a month on a dedicated (you could start on a $20 reseller , see resellerzoom) $15 a month on billing(Whmautopilot is newbie friendly,well kinda) and then say $30 a month on support (Kayako etc). You should budget around $300 a month if going for a dedicated or $100 on a reseller. Then you would be in a good starting position.
If you don't have the cash to at least do $100 a month, don't start getting into hosting,it won't be worth your time Imo.
You can accept payments by bank transfer or credit cards via Paypal.com, Moneybookers.com, 2checkout.com, Stormpay.com, Worldpay.com... etc.
If you designed your site then you can receive orders by using a whois and a form mailer script at starting. Or you can use a professional hosting billing software like Modernbill, WHMAutopilot, Clientexec, WHMCS, phpCOIN(it's free)... etc.
Customers can find your site by search engines(like Google) or hosting directories/forums. You can give your anvertise to these sites. Good luck.
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