Why is this not the solution?

[PredatoryCatgirl]

People will outbid everyone else just to resell the houses and make a profit, like the way houses were before the timer was added in but with extra steps

Flipping only works now because you can get the house for 3M. This eliminates that entirely. Flipping, even if it still happens, will have a severely reduced profit, and therefore less incentive to do it.