If speculation is the problem, then making expected return from real estate investments less than expected return from risk-free or low risk investments should

If speculation is the problem, then making expected return from real estate investments less than expected return from risk-free or low risk investments should fix it. Something like, if 10 or 20-year US Treasury bond pays more than you'd make being a landlord and you expect little to zero asset appreciation, then there is no incentive getting into real estate. And it's possible to discourage house flipping by introducing some sort of friction. Like a high tax of some sort that is applied only if you sell sooner than X number of years (let's say 5)