Sounds to me like you should be looking for a professional networking engineer instead of hoping a bunch of people on a freelance forum (no offense guys) can point you in the right direction. At the rate youre going you'll ending up doing a half ass job that has half ass results.

Aside from that you havent really told us what your network is for. Knowing what you plan to do is integral in designing your network.

Also what do you mean by "fair amount of cash"? $500, $5000, $50,000?

Are you planning to have a firewall? in your case I'd recxommend a hardware firewall. Cisco Pix firewalls are nice.

Who is running all the cabling? Yunno 60 cat5 cables will take up some space?

Are you sure all the computers wont be on the network at the same time? How can you be so sure? What if they are?

Too many unanswered questions.