This isn't exactly true either. Property taxes have no bearing on your real estate ROI. You always pay property taxes; if you're not paying them directly, you're paying rent which has property taxes baked in. If it's rental property, your tenants are paying the property taxes with their rent. My rental property outside of Madison had $6.5K in property taxes last year. My tenants paid $40K in rent. I still earned between 14% and 35% on my initial investment, not including free cash flow on rent.
The extra money that you put into your mortgage payment to pay it off early has an opportunity cost of being invested elsewhere and earning compound interest. Every investment advisor will tell you to put your money towards the highest interest rate. It's better financially to invest in the market and earn, on average, 10%, than pay off a 5% mortgage early. Paying off a mortgage early is a psychological benefit, not a financial one.
In your scenario, if you purchased a $500K home with 10% down ($100K) at 5% interest, in order to pay it off in 3.5 years you would have to pay an extra $8.2K/month towards that loan. If you invested $8.2K/month at 10% interest, you would have $414K in 42 months. That's $14K more than the $400K loan you paid off. More importantly, that $414K is growing almost $3.5K/mo at 10% interest, more than enough to pay the $2.1K monthly payment on the loan if you paid it off over 360 months instead.