Mortgages spark more bad advice than almost any other money topic. I’ve owned nearly 200 properties, from interest-only loans to a 30-year at 2.75%. I’ve also been crushed by debt and freed by it. Here’s my view: the cost of your money—not the headline interest rate—should drive every mortgage decision you make.
Why this matters is simple. You pay interest either way. If you borrow, it’s on a statement. If you pay cash, it’s the opportunity you give up. Miss that, and you pick a path that feels safe but drains your wealth.
The Rule That Changes Every Mortgage Decision
I call it the Cost of Money, or COM. COM is the higher of two numbers: the best return you can reliably earn, or the highest rate you’re paying on debt. That’s it. Use this and the fog lifts.
You always pay interest—either to the bank or through opportunity cost.
Look at a $400,000 mortgage at 6.11% for 30 years. The first payment sends about $2,037 to the bank and $391 to principal. That’s 84% interest up front. It feels awful, but that’s how amortization works. Early interest is high because the balance is high. Later, principal wins.
Now flip the script. Pay cash with $400,000 that could earn 5%? You give up $20,000 a year, every year. That’s invisible interest. Whether you finance or pay cash, there is a cost. The question is which cost is smaller—and which choice you can live with.
Why One-Size-Fits-All Advice Fails
Two loud camps try to run your life. One shouts, pay off the home fast with a 15-year. The other screams, borrow more and let the assets do the work. Both skip you.
The 15-year crowd means well, but the higher payment squeezes your cash. On a $400,000 home, the 15-year can be about $840 more each month than the 30-year. Then a surprise hits, and people swipe a card at 28% to protect a 5–6% mortgage. That is a trap.
The leverage crowd sees money as a tool. I agree—with a filter. Borrowing without COM, cash flow, and peace-of-mind checks is gambling. I learned that in 2008 when a chain of deals fell apart and my net worth cratered. Numbers on a screen don’t tuck your kids in at night.
The higher the emotion, the lower your financial intelligence.
Real People, Real Stakes
Friends of mine, Clark and April, were “asset rich” and cash flow poor. An advisor urged them to refinance a paid-off home to invest more in the market. Then they lost $600,000 in months and added a mortgage payment on top. We reversed course: paid off the house, reworked their loans for income, used proven tax moves, and found $32,000 a month in cash flow. Math plus peace of mind won.
On the other hand, I choose not to pay off my 2.75% mortgage. I can reliably earn more through tools I know well—properly structured whole life, parts of my business, and real assets I control. For me, paying it off would burn dollars I’ll never get back. Cheap debt plus reliable returns beats a paid-off house with idle capital.
The Fast Test I Use Before Any Move
Run this five-question check. It takes minutes and saves years of regret.
- What is my COM today—the higher of my reliable return or my highest debt rate?
- If I shorten the loan, do I create a cash flow squeeze that pushes me to high-rate cards?
- Do I have six months of expenses liquid after the decision?
- Can I point to a reliable return, not a hope or a tip?
- Will this choice help me sleep? If my spouse hates it, it fails.
Here’s how that plays out. If your mortgage is 6% and your best reliable return is 4%, prepaying makes sense. If your mortgage is 2.75% and you can earn 7% with low risk that you understand, keeping the loan likely wins. Simple, not easy.
Common Traps To Skip
Small tweaks can save big money if they fit your COM.
- Bi-weekly “programs” aren’t magic. One extra payment a year does the same thing without fees.
- Choosing a 15-year for the lower rate can backfire if it risks 28% card debt.
- Paying cash with no liquidity can force a high-rate loan later when life happens.
Use flexibility as a feature. A 30-year with optional prepayments can beat a rigid 15-year if you need room to breathe.
My stance is clear: Let COM lead. Back it with a cash cushion. Pass the peace-of-mind test. Ignore the shouting.
Choose the cost you can afford and the life you can enjoy. Run the math, check your gut, and make the call you can defend when markets swing and life gets loud.
Final thought and call to action: Stop letting gurus pick your path. Calculate your COM, build six months of liquidity, and decide with both numbers and nerves. Then create a life you don’t want to retire from—even though you can.
