RDP for Windows 7 Home

You can't it is not part of the o/s.  You can use alternatives i.e. logmeinfree, real-vnc, teamviewer to accomplish the same thing though

Very true the above.

Alternatively, since you have a business need, upgrade Windows 7 to Pro. This will solve your problems.

Windows Home has never been adequate for business needs.

.... Thinkpads_User

Okay thanks - do any of these work so someone could login when needed, so if there is a pc on the network, they do not need to initiate the session?

RDP works better (but you need Pro to run it). You do not need anyone at the other end so long as the system is on.

.... Thinkpads_User

All 3 suggested can work unattended. For teamviewer is called teamviewer host, for vnc is vnc server, for logmein I have no idea :)
I don't know what can you use for free though...

@thinkpads_user: for home users I found RDP to be more trouble than worth. You need to activate it, open the port in the router, set the firewall to only allow connections from specific IPs (preferably with a VPN) or you'll find automated password tests trying to force your password within hours.

HTH,
Dan