so far from what i hear you don't have to buy a domain for a reseller account but if you want a definitive answer send a ticket to support. This whole thread is
garbage consisting of the same questions asked over and over again with nobody to answer them because it's too time consuming to answer the same questions over and over and over again...
http://desk.surpasshosting.com
anyways i don't see why you would need a domain name for a reseller account... but if you do end up wanting to use one later on you'll have to wait till jan 2007 to apply it to your account.