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Use a separate wireless access point plugged into the home hub Ethernet port. You can set a different SSID and password for it.
Unless I am mistaken, if you have sharing enabled on your home network your guests will have access to your home network even although they have used another access point and password.
If you want to restrict access to your home network from the Guest wifi then you will need a replacement router - enabling Guest Wifi on a second router (or just having another SSID) typically doesn't restrict access to the home network.