I actually agree with allowing multis, but only by request (you can use a system for this). Then transfers between legitimate family members is fine, however you get a % penalty for doing such a transfer e.g. cash transfers 20% penalty, crystals, 25% etc. This allows the genuine households to have more than one account well discouraging them from helping each other all the time. The only downside is that staff will need to review logs a lot more to spot any feeder accounts if anyone attempts to cheat your system. A search feature built into the logs will make it easy to see all multi transfers amongst households, and therefore spot any feeder accounts.