Third Party Mirror server needs

We are planning on developing a small multiplayer game using mirror, from what I understand, we need to provide our own host server and we have an oldish computer and were thinking about turning that into the server. Are there requirements for the having a host server that we should be aware of? (like no less than x amount of ram etc.) additionally here are the specs of the old computer (it's a laptop) please let me know if it would work decent.
CPU - Intel I7 4700HQ
Ram - 12-GB
GPU - Nvidia GeForce GTX 860 M

 

This really depends on your game, without knowing anything about your game it's pretty hard to say what the minimum requirements are.

That said whatever the minimum requirements are, the specs you told us are more than enough. But you should think twice about using a laptop if you want the server to run 24/7, depending on your game a cheap AWS instance with a headless unity instance might be enough.