I preffer the reseller account of
TargetDomain.com (same as WWD reseller, but cheaper).
There is a fixed 89$ fee per year, but you get a compleete customizable ready to go turnkey website packed with much more services than only domain name registration (e.g. hosting, Search Engine Optimization, submission, SSL certificates, etc..)
With every domain registration there comes a bunch of free features like forwarding/masking, DNS/MX control, parked/for sale page, etc...
You do not have to pre-pay any services as in many of the other resellers as the reseller account incorporates real time Credit Card processing for your customers.
Support, maintanance, etc.. will be done by them, so that you can concentrate 100% on marketing your service.
You as reseller can set up special discount accounts for you or your customers to let them buy the services at discount wholesale prices.
From time to time they have special promotions with rock bottom prices.
More info
here.