A MacMini comes without a keyboard.

Have you considered making use of binary compatibility and emulators? You could do the following on a FreeBSD system: enable Linux binary compatibility, install Linux shared libraries, install a Linux version of VMware Player (which is free), then run Microsoft Windows (and any desired applications) within the VMware emulator. Avoid virus/spyware infections by isolating different Windows installations and, if necessary, working on a throwaway copy.

That would give you a secure system with all the Windows software at your fingertips, quarantined. All you need on the FreeBSD system is extra diskspace and memory for the virtual machines.