It could be done with ESP32 and LoRa, but that would be ridiculous. We built a mesh network using that in my neighborhood, but I am telling you, it is not worth it.
Just use WiFi. Everything is already done for you. Leave the network open and use a simple SSID. Add APs as necessary. There are millions of tutorials and videos about this. It doesn't get any easier.
edit: Also, you can find routers at almost all resale stores (Goodwill, Salvation Army, etc.). Last time I was in the USA, I bought a bunch of them for $5-10 each (and they were most recent units --not outdated crap).