Thank you.
I ended up going with reseller, specifically digital ocean as they had a whmcs plugin.
It turns out virtualizor has one as well so this was very helpful! http://www.virtualizor.com/wiki/WHMCS_Module_to_create_Reseller_Accounts
You want to become a reseller? Or own your own infrastructure and sell VPS from it.
If you want to become a reseller then there is a lot of companies, Softlayer, SingleHop, VPS.net etc.
If you want to own your own "Cloud" WHMCS and Cloud Reselling is quite complex. You can use SolousVM or there is Virtualizor (http://www.virtualizor.com/) - but these are mostly for VPS NOT Cloud.
Cloud goes beyond VPS/VM. There are a lot of things you can do in Cloud, for instance develop a cluster, have various compute node using a single storage. etc. So, when there are multiple compute node sharing the same storage, you will be able to move your VM's without any hassle - else you need to copy the whole image across.
You can create a network for load balancing etc.
Then come IP management etc. If you are looking for all these features then you are looking at Apache CloudStack or OpenStack. Unfortunately I am not sure if they are integrated with WHMCS.
Let me know if you need further clarification.