in germany it is very common, that you get more than one domain for free, when ordering a hosting package. I feel like germany is the only country where this is so.
At normal you have, say 3 Domains for free, you can register the 3 Domains at order time, or order them later. But always free, because they are billed with the normal hosting package.
We have tried many things and workarounds with WHMCS and its always very unwieldy for the customer to get his free domains.
It would be nice, when the customer can see in his account, how many free domains are used.
It should be configurable what TLDs are free. e.g. only .de Domains, or mixed like .com/.net/.org Domains.