pfSense router - one port?

If I make a router from an old PC and use pfSense, will I be able to only have one ethernet port on the router/pc and use an ethernet switch to connect the router to the modem? Or will I have to upgrade the NIC on the router/pc to have 2 ports?

I have been using pf sence for a month now and its great, now, I would assume that you can make it so that pfsence justs side lines the network managment, but I dont remember being a setting available to have 2 interfaces over 1 nic , I wouldnt bother fiddeling with ot like that anyways 2 nic makes life sooo easy when setting it up