Are there any minimum WiFi requirements for a Maestro?

You need a wired or WiFi ethernet connection from the Maestro to the radio. Internet is only required for SmartLink (i.e. remote operation) or for upgrading the SW/FW.

The easiest setup is to have the radio, PC (if used) and Maestro all plugged into your modem/router (or a network switch plugged into the router) set up to provide DHCP-served IP addresses (most routers are set up this way right out of the box). Using wired ethernet provides the best network performance.

I don't know what the WiFi requirements are, but any reasonably modern WiFi setup should work. Note that the closer you are to your neighbors running WiFi on the same frequency bands as you (2.4 GHz, 5 GHz), the more likely you are to have latency and/or dropouts due to channel contention. In my case, I am on a 2.4 GHz WiFi, and I can see TONS of neighbors' WiFi signals. I can (and do occasionally) run remote from my living room using WiFi, but 99% of the time I run Wired ethernet to a switch plugged into my router. No matter how congested WiFi gets, I have a consistently good experience with my set up.

If you really need to go with WiFi, I would suggest trying it out with what you have. If it is unacceptably slow or has problems, look into a more robust 5 GHz WiFi system - I don't think they are prohibitively expensive ($100 USD or so).