Checkout enom and tucows for selling domains. It's fairly straightforward to get setup as a reseller and start using their API's to sell domains white label on your site.
My email is in my profile if you have any questions. I'm an enom reseller and have no complaints.
Yup, we're using Tucows (OpenSRS) to sell domains on Strikingly right now, and yearly users will get a domain for free (helps increase the conversion). I haven't tried enom but have heard great things about them too. Any reason you chose enom over OpenSRS?
My email is in my profile if you have any questions. I'm an enom reseller and have no complaints.