A little old, but here is some free market research for anyone else coming across this reply. If you have not seen them yet, the 2 main solutions resellers use for delivering VPS are cPanel and a solution from Plesk called SolusVM: both deliver an entire dashboard for customer onboarding, provisioning, application installs, and billing.
If you are looking to do this with VMware solutions (since you are in a VMware Forum), vCloud Director (vCD) is probably best but is unlikely to support the limited resources you described, and would require customizations after deployment (and you need resources for vCD to run on).
Finally, here's a slightly dated article that lists several free solutions as well:
https://crgsoft.com/8-best-2019-vps-control-panels-free-and-paid/