30 year debt at 3% is better than zero debt at zero percent? Help me with that math?
Yes, in some cases, it is better. Banks make a lot of money off of the 'keep the spread' difference. They pay interest at 4% and loan money at 7%, thus keeping 3%. If a person borrows $300k at 3% for a home purchase instead of liquidating $300k of assets AND the assets grow faster than 3%, then the individual would be using the OPM (Other People's Money) principal to make >3% and keeping the difference. Does that help you with the math? It's not for everyone as there is peace of mind to factor in, not having a mortgage payment makes some people feel very good about themselves, in today's environment (6+% mortgage rates), it's not as simple. But, a couple of years ago at 3%? Kind of a no-brainer. For instance, if you had $300k in the S&P 500 index in 2023, you'd have made about $50k while paying $9k in interest. Seems like that's a pretty good deal. Of course, the market doesn't always go up (see: 2022) but, over the course of a 20- or 30-year mortgage, if the interest rate is low enough, you're a heavy, heavy favorite to have more money having the mortgage than not.
Also, some people get to deduct mortgage interest, thus making the 'net' cost of borrowing even lower. Finally, having a home paid off is great. But, only if you have enough other assets to support your lifestyle. You can't take home equity to the grocery store. If you use home equity to buy a car, pay for college, take a great vacation, you are, in essence, putting a mortgage on the house.