Do I need to secure my home network with a guest WiFi?

A separate guest Wi-Fi network is the best solution - it isolates your main network from devices you don't trust. Most modern routers have this feature built in. You just set up a second network with its own name and password, and your guests connect to that instead of your main network. That way they get internet, but they can't access your printer, NAS, smart home devices, or other sensitive stuff.

This is really important if people regularly come over to your place or if you share your Wi-Fi password around. Especially if guests have smartphones or laptops that might be infected with malware - an infection like that could otherwise spread to your devices on the main network. Plus, if someone ever writes down your password and misuses it later, you can just change the guest password without disrupting your main connections.

In your router settings (usually 192.168.1.1 in the browser) you'll find the guest network option under Wi-Fi or Wireless. Just enable it, set a name and a strong password - done. It costs you zero extra in security for your own devices.