I have 2 small companies (4 and 10 users) that are going to share a small suite to cut costs. Both are on their own Windows domains and will be sharing a single internet connection. Budget is non-existant so trying to do this as cheap as possible. They trust each other but still want to keep all of their own files separate. Plan is to put them onto one subnet, use static IPs for everything. Since logon domains will be separate, that should give basic security. They will have a single workgroup printer for the entire office to share. The only available network equipment is a couple of low end ethernet switches and a wireless router to work with so multiple subnets or vlans are out of the question.
Any problems with running this scenario? DNS be a problem?
Another thought was to utilize company A's SBS server as the only DC and company B's server as a standalone file server and use permissions to keep files secured. This would eliminate issues between 2 domains.