Do I need an ethernet switch and a hdmi switch? Ethernet shares the desktops and HDMI shares the display? I have only 1 monitor.
Do you have a router? Or router built into modem?
If you don't have it, you'll need a router too.
What monitor do you have? Does it have multiple video inputs?
If it has, then you connect one pc to one video input, second pc to second video input.
Switch between inputs with buttons on monitor.
If your monitor has single input, then yes - you'll need HDMI switch also.
Make sure, both your pc-s have HDMI output.