I did exactly this with PC Connection and got into the Open license program. What's great is that you get 50 activations out of the box, so while it's a bit of money up front, it effectively allows you to use a bunch of systems and VMs internally without worry. No one is going to say anything about this especially if it's for personal use.

If you were supporting multiple users in a small business environment definitely make sure you buy as many Windows SKUs as you have end users to be compliant, however.

All of this becomes moot once you have >25 clients; then you can transition to using volume licensing and it's essentially unlimited. It still tracks it though and Microsoft can ask to look at it, especially if you change from Open to Select or some other volume pricing agreement, so keep that in mind.