The real issue or the
root cause is SE creating
artificial scarcity with the limited ward housing system.
Every issue we've have had with ward housing over the years has been due to this artificial scarcity. Multi-house owners would not be a problem if there was a unlimited or near unlimited supply of housing if SE had implemented a fully instanced housing system right from the start.
RMT house selling is profitable because of the artificial scarcity. If there was no scarcity, there would be no RMT house selling.
Nearly every major MMO which has gone with the route of limited housing has faced similar problems like with FFXIV's ward housing. Here's an article which explains why limited housing in an MMO is a bad idea:
https://www.gamedeveloper.com/busine...housing-crisis
Players need to stop fighting amongst ourselves and ask that SE do better.