Renting out things has always been a big issue on civ servers.
I think there should be a permission node added to namelayer that adds a person to the group for a duration. This would allow them to use the group, but automatically remove them after so many hours, days, or weeks.
This could be tied into itemexchange (provided itemexchange could be updated to allow for namelayer group addition output) somehow to allow for people to automatically purchase temporary access to say factory rooms or rent out a shop area.
Once this and the itemexchange changes were added, taxes could actually be an easy thing to do on civ servers.