Let me quote from the posting rules ... in case you missed it when you failed to read them.
10. Don't Post Homework Questions
We will close any threads asking for help on assignments. We've done our homework, you do yours!
In short ... You may consider this an official screw-up.
Now, in answer to your question:
Given your level of expertise, and your predilection for taking the easy way out and getting others to do your work for you ... I recommend contacting a local IT company and have them come over to your fictitious company ... and install a MAC server running whatever version is current. Then I'd say replace all your workstations with MAC minis.
Then, as an afterthought, go out and purchase a text book on system administration for all three competing sytems, Windows, MAC and Linux.
And then, from that point forward, whenever there is a problem, you can call those friendly MAC guys to come to your company and solve your problems for you.
Then you get to pay the bill.
And ... in the fullness of time ... when the inevitable budgetary crunch has you up late at night worrying instead of sleeping, you can spend a few evenings/nights reading the afore-mentioned textbook. And sooner or later ...
it'll come to you.
EDIT: By the way ... all ribbing and kidding aside, for a start-up company who/which does not have the benefit of a highly competent and motivated techno-dweeb on staff or a willing service/slave person they can trust and call on in times of crisis ... the commercial software/service contract really isn't such an outlandish idea. The business of a business ... is its business. Not forever mucking about in the file server room/closet trying to solve technical issues, most of which will very likely be self induced out of ignorance and false economy.
That's why those silly little IT/tech companies exist. So you
-- as a business person -- don't have
to be an expert.