I'm not sure there's such a thing as a housing lemon (except maybe a house so infested with mold it has to be torn down, or something built in a place where nothing should have been built in the first place). There are houses that require massive investments (foundation, roof, plumbing, sewer) but those are all knowable. The simpler answer is probably that your models don't work if your model causes you to take action that changes the market. See the SciFi paradox of predicting the future causing you to take actions that change the prediction of the future. For example what happens to prices when you add an algorithm that is REQUIRED to make a certain number of purchases a month? (I'll give you that one for free. Prices go up A LOT) What happens to the cost and availability of contractors when demand increases by 20% (same answer as above) Now feed those things back into the model. Add in the fact that market rate changes based on the number of aggressive algorithmic buyers operating in the area and that you're not going to bid on your own sale (I hope!) CRAP! Now those actions we took before are predicted not to be cost-effective! Obviously. Remember the first lesson of thinking ahead, kids. If I do X, Y will likely happen.