I have a client that would like to control what websites his employees
can go to and what websites they cannont.  He wishes this control to
be on an IP basis with a password override.  Furthermore he wishes to
prevent downloads from websites and e-mails.  He has 6 computers on
his network so he is looking for an inexpensive solution.  My
questions is what can he do that is both inexpensive and effective?

hello, you can setupo a firewall proxy using an old server with linux
and iptables. Inside Iptables you can setup all the policy you need
for the internal lan or import blacklist that are public.

For preventing downloads you can semply setup rights in the lan
Claudio