Usually, lol. I just keep thinking of what one of the experts on Experts-Exchange tells me. Most of the problems in networking stem from the network and OS not being set up properly the first time.
Networking is a lot like Scabies. I know, weird. But, John Stokes, I believe it was, stated a long time ago that Scabies was the easiest and most difficult diagnosis to make in dermatology. I think he is right. Networking is the same. It is simple at times, but it can be overwhelming at times. Another favorite expert of mine always tells me something his computer science professor told him: "99% of the time, the problem is DNS related." You can Google it.
No matter what you do, if you take my advice on the following you will be happy. If you are going to purchase a server with an OS, go with Small Business Server 2003 or 2008. You will absolutely love it. Of course, to get the full benefit, it will have to be set up correctly. And, you will need RAID, etc.
Exchange Server (which comes with SBS and can cost nearly what another OS cost on its own) will be beneficial and something you will enjoy down the road. But, Sharepoint will be something that ONLY SBS offers, and you will absolutely love it and, even better, your staff will love it.
I forgot to tell you one thing. You should tell the IT person what your needs are but also give him or her a budget. That will help tremendously.
I look forward to hearing your progress as your progress through the steps of building a network.