This question already has an answer here:
I'm trying to choose a antivirus solution for tiny non-profit organization (5 workstations, no server).
Is it possible to buy licenses and run Microsoft Forefront Client Security Agent on these workstations? $12/year per device license is a good price.
But if I have to purchase Management console for $1000, which reporting features I don't need, and a server, it won't make any sense.
Microsoft Security Essentials would suffice, but it's impossible to buy it for non-personal use - and free license does not allow it.