Is it possible to "share" a LAN connection in two separate lines?

Hello Sevenforum and sry in advance is this is the wrong forum for this question.

Is it possible to create 2 separate Internet connections within 1 local area network?

More specifically, let's say i own an Internet Cafe which only have 1 local area network with a Wireless Internet connection. Within this wireless LAN i would want a secure line, in which i can upload/download information from home to my computer at the internet Cafe, while at the same time having an open line for the visitors to use. But the visitors cannot use the line and be able to connect to my "part". Also, i am only able to use Wi-Fi connections, so no cables.

Is this possible, or is it easier to create two separate LAN with 2 separate Wi-Fi connections?

Thanks! :)