A quick google search told me that the expected ROI of investing in the stock market is roughly just under 10% That's admittedly a bit higher then I had anticipated, but quick scanning of their numbers didn't show any clear flaw with it. There is of course a decent risk in stock investments, but for a large enough company with enough money that risk can be adjusted and accounted for.
In comparison a quick search for the rate of secured loans, using either a home or auto vehicle as collateral, showed interest rates much lower then that; around 6-7% for home equity and I even saw a few places advertising less then 3% for auto loans - though that number seems so absurdly low I suspect they must be hiding something in their fine print.
I understand that a loan with collateral are lower risk then the stock market, but is the risk really so much lower as to accept only 2/3 the expected ROI from the stock market? Is there some other reason why secured loans would be preferable to just investing in the stock market? Is Google's expected ROI claim for the stock market too high? Are banks expecting to make a profit from late fees or repossessing collateral to make up the difference?
Put in another way, if we pretend I had a home is there any reason I shouldn't go out and get a home mortgage just to invest the loan in the stock market, other than that minor detail that I might end up homeless? Joking aside with my current nest egg I could be pretty confident I could manage even a fairly significant crash in the stock market without risking defaulting on my loan, my excess income alone should easily be able to cover a monthly minimum payment even if I lost all my investments. So if I'm comfortable with higher risk for higher expected ROI is there a reason I shouldn't be mortgaging my (non-existent) home right this second?