So, I've finished all the three wings on all three houses (complete with cellar in all three)... and this achievement hasn't popped. I've looked online and received conflicting info as to what's needed to get this. Some say you need all three houses to be fully furnished, others say you just need all three houses with three wings unfurnished. This is a little frustrating as the thought of having to start a new game solely to get this achievement isn't really appealing.
Any advice or info about this 'glitch' or ways to get this achievement would be appreciated.