I have 2 mac mini's and was wondering if I could use both of them together as 1 server. It makes it easier when designing to have just one server instead of connecting to multiple servers. Thoughts?
So you mean an Xcode server? A file server? Both? There's no way I am aware of to combine two Macs to act as a single Xcode server. A file server yes, but it would be two shares, one on each machine.
You can as long as both either have a Firewire 400,800 or Thunderbolt connection. You can connect them both as Firewire bridge or Thunderbolt bridge; preferably Thunderbolt 1 at least for increasing file server capacity. In my case, I bridge both my Mac Mini and Macbook Air together to act as an added file server, USB3 bridge and as a Quicksync station for my Mac Pro using Davinci Resolve. My MB Air is not connected to Ethernet -- it uses the Mini's bridge to connect to internet. So using say a Mini 2018, you will gain 3 extra USB-C Thunderbolt 3 ports and 2 USB 3 ports by bridging 2 Mini 2018 together, but any Mini will do.