One plan cost around $250/year. Under this plan you will get a fully branded website with free domain name. Everything is ready and all you have to do is market. I think the profit margin will be somewhat less. This plan is good for beginners. Let's do the calculation to find the profit. $250/year means approx $20/month. Sell 10 domains/day Profit is $20/day (profit per domain $2) i.e., $600 per month.
Another plan is API reseller. That is if one has already a webhosting or domain registration business or web design business one can integrate this reseller plan into the existing business. The profit is a bit more in this case and one has better control over one's business.
There is another plan but it is costly for beginners. The profit margin is very high in this case. But one has to deposit $5000 or $10,000 (please correct me if i am wrong) with Enom.