one of the main issues in the logic would be volatility and longevity of the investment in question. quite doable, and you could even make more than that if you were good with your investment, but nothing that is currently at 10-12% is an entirely safe investment, so there is the element of risk. but, even if it works exactly as stated, with the time value of money, the value of that is much less at NPV, so it comes to the issue of how much screwing around is worth a minimal return?
seeing as how the s&p500 is under 8% for the past year, it would be hard for johnny non-investor to make any money at all (if not lose money) with this method.
yet another issue with not having the downpayment on your house is that you are going to behind with building equity on your home should you need to sell it.
im really tempted to write a lot more, but i told you before that i wasnt thinking bank talk since i have today off, so im leaving it with these few scattered comments.
time to have a beer and forget about work lol.