neighbourhood isp

Hi all.
My first post here.

I am looking at setting up a neighbourhood isp and need some advice.
Basically the plan is to have a server based on Kerio Winroute firewall. I
have a licence for and am expierenced at administering it.

The problem is this. How can my customers / neighbours connect to me.
Basically the only option is wireless. This i thought is pretty simple -
just stick an antenna on my roof which can see just about everyone else in
the neighbourhood and then have it bridged to each customers ap and down to
their computer.
Unfortunatly, if my customers are the way i expect them to be, they have
more than one computer and the web login to kerio doesnt always work well
and lets things like msn through without counting their bandwidth.

I also dont want someone else setting themselves up as a client (WEP or WPA
will not be used at all!!!) and then having their own proxy server on the
network to their isp to bypass my nat gateway / kerio. I also dont want
users able to connect to each other.

Next i thought VPN. Kerio has a vpn server built into it and i thought that
if i had a router at the client end, routing traffic back to me, that would
stop them talking to each other, but then only a few computers on the client
network can connect through their router.

So i guess my question is this:
Does anyone have an idea on how i can have my clients connect to my server
on the network, while keeping their network private, and not being able to
directly communicate with other users on the network. eg. 192.168.1.5 cannot
talk to 192.168.1.6 without going through the gateway and having their
access authenticated?



Thanks,

Ray Taylor