> I think the idea is that if you rented that whole time and invested your money in the stock market you'd be just as well off The OP said their mortgage is al

> I think the idea is that if you rented that whole time and invested your money in the stock market you'd be just as well off The OP said their mortgage is already lower than rent, which is typical, so it is the homeowner who has extra money left over (compared to if they were renting) to invest every month. The renter has ever-increasing rent swallowing up any raises, so not much left over to invest.