If you can afford it, I think DirectAdmin has lifetime license for 300 USD or something like that and it can be transferred between different machines. Free solutions, if you're going to use it yourself then it's fine I guess (but it's not set and forget), but if you're going to hand out stuff like cpanel access etc to your clients then it's probably not such a good idea. I mean you get what you pay for. Of course DirectAdmin is not perfect and most of custom stuff still has to be done via console (like certificates, php modules, etc).