konung PRO said about 2 years ago on Remote Development :
The information about only being charged when droplet/vm is in use, is incorrect. Just shutting it down is not enough.

From https://www.digitalocean.com/pricing - FAQ Section. 
Why am I billed for powered off Droplets?
When you power off your Droplet, you are still billed for it. This is because your disk space, CPU, RAM, and IP address are all reserved, even while powered off. Therefore, charges are made until you destroy the instance.

Having said that, I will use this idea, to setup my kids with remote dev on their chromebooks, with VMs running on my home NAS device. 😀 ( Then hit them with unexpected bills 😈)