Monitoring a Network

I am looking for a way to monitor my home network. I am the one who pays the money to run and operate the network, but I have become suspicious about what it is being used for at times.

I do not know much about packet sniffing, but I know it is possible using programs like wireshark. However, I am looking for more of a longterm solution. If at all possible I would like something that is free.

Thank You for your help.