The following require some understanding on your part, so please do your homework and consult your financial advisor.
(a) Maximize your cash by investing in high yielding money market accounts (offering say 6% per year for one year, offered by FNBO Direct, www.fnbodirect.com ): Did you know that most people have money sitting in savings account earning 0.5% ? Why not earn more than 5.5% on your money ? If you put $100,000 in such an account, your interest at end of year is $5000 (instead of $500).
It takes only 10minutes to open such an account(completely online application too)
Bankrate.com has links to many of these banks :
Bankrate high yield CDs
(b) Borrow at 0% through ( these credit cards ):
If you have already maximized your passive income, with the high yield savings accounts, then you can even carry on some good debt on your credit cards (at 0%) and invest the cash from credit cards in high yielding money market accounts. This shows how to do this.
Borrow at 0% APR credit cards, and invest in high yield CDs
Also, most of such cards have a 1% cashback bonus on purchases.
(c) Why paying rent/mortgage etc thru a 0% APR credit card is great :
If you are paying rent per month thru any credit card, there might be a convenience fee of say 1.5% charged by apartment owner or bank owning your home.
But even then, -1.5% + 1%( credit card cashback bonus) + 5.5% (invest in a money market account itself) = +5.0%.
If you pay $20000 in rent per year, the above shows that you will make/save $1000 on it, if you can do the above.
(d) Why buying car etc thru a 0% APR credit card is great :
for the above same reason
(e) Online Insurance etc is best : I found insurance at Esurance.com to be cheapest, by around 50% compared to what I was paying earlier. Check out Insweb.com too.