or is it really true that getting someone else to pay off the borrowed investment capital drastically increase the profit margin? It is like someone paying for the margin to buy stocks while the account holder is reaping all the profit…
Yes, someone is paying your expenses and you are reaping the appreciation/cash flow/tax advantages. This is generally called leverage and it is how real estate can be used as a powerful way to make money.
However, as the calculation above shows, it is not as easy as you think and it requires a lot of knowledge to do.