Also, desktop systems don’t usually come with WiFi network adapters; they typically come with wired Ethernet adapters. In general, wired Ethernet is much better than WiFi anyway, so if you have the ability to run an Ethernet cable from your desktop to your internet router, that’s the way to go. If you need to use WiFi, you’ll want to make sure to add a WiFi card (or perhaps USB adapter) to the system you buy.
You said you already had a display. Do you also have USB keyboard and mouse you can use? If not, that’s something to consider, too.