There are several points in your article that are simplified to the point they are misleading — I’m hoping to help clarify a few points to both help you understand why that is the case and so that your readers wont take decisions on misleading information.

For example, your statement, “*You see, I like to say that not having to pay 4% in interest is equal to receive 4% in returns*” is incorrect. **A mortgage (or student loans or other personal loans) accrues compound interest which is more complicated than the simple interest that you’re alluding to.**

Also, you said: “*So if you paid off the mortgage you have $4,000 more the next year because you don’t pay interest any more. And that is 4% of the $100,000. But instead of paying back the mortgage you can instead use the $100,000 and buy index funds.*” **That is also incorrect. Your mortgage monthly payment is determined by (1) your loan amount (2) your interest rate (3) your loan term. A $100,000 mortgage at 4% and 30 years = a monthly loan payment of $477/month = ~$5,700 per year. A 30 year mortgage will also pay over $62,000 in interest if follow the schedule for 30 years. If the loan term is diminished to 25 years, then = monthly loan payment of $527/month = ~$6,300 per year and nearly $52,000 in interest if follow the schedule for 25 years.**

The decision about whether or not you should put an extra dollar towards your loans must be evaluated relative to the interest you would save. I also do believe that it is not always optimal to put an extra dollar towards loans, and I have both written on the topic and created a financial tool to help people determine the answer for themselves. I have found that it is a matter of optimizing the value of your money towards interest saved AND it’s a matter of figuring out the minimum return you need in the market. For example, I ran the numbers in my tool with a hypothetical example. If someone has around $2000 of disposable income, if they divert their funds then they would need to get at least a 5.03% in the market in one optimal scenario — BUT this number should actually be higher because the person will need to account for taxes.

I would be happy to talk through this with you more and answer any questions