Local area network connectivity via cable modem Wi-Fi
Addresses assigned via DHCP
Network consist of computers and a wireless printer
Operating system windows 10
Objective
Have all the computers be able to access resources on each other and the printer
Only one of the computers in the group be able to access the internet but have its files protected from internet

How is this possible

Thanks for any help you can land

It may mean inserting your own router between Comcast and the rest of the internal machines. That's how I handle it.

Comcast router/firewall didn't do what I wanted it to do out of the box, so simply adding a new router between that Comcast internet connection and my home computers gave a lot more control.
Get a decent one and it will work for years.

If you really want to make all internet traffic route through one computer and have that computer protected from the internet (as much as is possible) I suppose it could be a software firewall .. but a separate router/firewall seems like a simpler and likely more robust solution.

/edited for simplicity

thank you