Wireless Access Point that connect to a WI-FI and create another Wifi

Hi,
I wish to buy an access point that will allow me to connect to a certain wifi and then allows to create another wifi(another routed network) that allows me to access the internet from the main WIFI .

Basically I have a big wifi (lets call it BWIFI) that has internet access and I want to setup another wifi (lets call it CWIFI)network that connects to this main WIFI to get internet access but users from bigWifi are not able to access the network resources from CWIFI . Is it possible ?...

Wireless Access Point that connect to a WI-FI and create another Wifi