@paulalex First off, welcome to HubSpot CMS!
I’ll typically build it in the client’s design manager in a new folder/theme. Then when it’s ready to launch, if you’re keeping all the same page URLs you can stage each page. Or, if it’s a completely different URL structure you can just create brand new pages from the templates. Once all your pages are staged/created, publish them to production and flip the blog template and various other system pages to the new ones. That’s basically it in a nutshell.
We just use individual user accounts at Kelp. 