Will your customers be technical in nature? Will they
do their own administration through the control panel
or are you planning on setting up their email accounts,
etc?
If you are handling everything yourself, you could just
get a small hosting account that supports multiple domains
and just go that route. If your hosting efforts produce
some growth you could upgrade to a full featured, but
higher priced reseller account that will give you the
ability to compete against the 1000000s of other
resellers out there.
Good luck.
elPresidente