I have a friend that owns a small office - 5 people working on windows 10 desktop. He recently told me he is constantly dealing with viruses, PC slowness, etc. He never instituted any kind of security policies etc, he simply set up the workstations as regular windows PCs and gave them to his people. They installed whatever they needed and it sounds like they have full admin access. I'd like to help him lock everything down as tightly as possible, similar to a restrictive corporate environment, with daily offsite backups of their core data. I have some general ideas on how to do this but I'd like to follow some best-practice guidelines so I get him to a good place as once I hand it over to him I won't be around to constantly fight fires for him.
What's the best path forward? Does he need to relicense his workstations (I believe it's regular Win10 Home)? Subscribe to 365 and use Onedrive? Is there an 'industry-standard' series of steps for a typical small business that wants to protect itself from inadvertent issues caused by end users installing random apps and extensions?
Thanks for any pointers!