What equipment do I need to connect multiple devices to a limited network

I live in a room where there is an established commercial wireless network where you pay monthly to access. You are limited to a maximum of 4 devices or required to pay more per month. Is it possible to buy a WiFi repeater/router that can connect to that network and rebroadcast that out so that I can connect multiple devices to the router rather than the network? If so what is the best equipment to buy to achieve this? Thanx