No if you signup for a reseller account you will be allocated a pair of IP addresses with nameservers setup at no extra cost. So if your domain is named yourdomain.com you will receive ip addresses (in the same subnet) corresponding to ns1.yourdomain.com and ns2.yourdomain.com. You would then change the nameservers for the domains you host on your reseller account to those addresses.
You will only really ever need to buy static IP addresses to go with SSL certificates.
Andy
