I only know of the read only or full access options for sharing (window explorer/ righthand button/sharing). These can be set according to a password.
But you seem to be wanting to create two separate lans with restricted access. Sorry I don't know how you do that.
But it seems odd that you want to share the internet access wiht your neighbour. Apart from vulnerabiliies etc, it is looking like you will end up with very little bandwidth each.