how to share my wireless internet access but not my files without using ANY security measure just WAP. network splitter?

how to share my wireless internet access but not my files without using ANY security measure just WAP. network splitter?

what I'm trying to achieve here is to be able to give my student neighbor access to the internet using the wireless side of my DSL router but I wouldn't like to have to setup encryption/privacy in any of my intranet wired XP/Ubuntu based workstations or my NAS