If you're going to go full economist, the correct use of debt is whenever the expected value of having something now instead of later exceeds the expected lifet

If you're going to go full economist, the correct use of debt is whenever the expected value of having something now instead of later exceeds the expected lifetime cost of servicing the debt. So it would be very reasonable to take out a loan for a car or a house, especially with interest rates around 4%. It might even be reasonable to take out a loan for furniture or a TV, but fiscally responsible people will usually have enough cash to pay instead, so in practice most responsible people don't take out loans for TVs. By the way, houses historically did not appreciate at high rates. The recent dramatic appreciation in housing prices in big cities is a giant blip in the data. You shouldn't bet on housing appreciating so well, and you shouldn't buy more house than you will use or rent. (If you think the increasing importance of big cities will automatically mean higher prices, ask homeowners in Tokyo how well that's been working for them.)