Costs are downright reasonable:
* Mountain Lion operating system upgrade: $19.99
* OS X Server app: $19.99
Unless anyone objects, I'll create an Apple ID based on firstname.lastname@example.org
and communicate the password somehow to infra.
While the sshd access has been hacked up to support the pubkey authentication required by infra, the Screen Sharing functionality uses the regular account passwords. So even if the upgrade hoses the former, the latter should continue to work.
Upgrade tips for the bundled Apache: http://support.apple.com/kb/HT5382