if you rent out a 1.3Mhs Scrypt contract for 0.008BTC right now accoridng to coinwarz you can mine 0.012BTC if you mine GPUCoin. You simply have to find the most profitable coin to mine within that 24 hour period and you will make a profit. We are just a service for that.
You're glossing over a whole lot of issues that will definitely NOT get you .012 BTC.
First, let's start with multipools. They all use variations on an algorithm to mine the most profitable coin. When that BigAssMiningPool(tm) suddenly starts slamming the coin you'r mining, the difficulty jumps significantly. Suddenly, that .012BTC coins has become a .005BTC coin. To avoid that, you'd want to mine coins that aren't in these pools. But therein lies other problems.
Aside from pool induced variability, there is also exchange variability and liquidity. Most of these coins make penny stocks look stable by comparison. Coins with low volumes can have massive swings in price. Low volume coins also mean you can put a sell order out there and have it sit for days (or longer) without filling. Due to the this variability, just because a coin is profitable to mine now doesn't mean it will be five minutes from now, and with all the anti-pool hopping logic out there you can't make anything switching between coins at that pace.
So that leaves you with the multipools or mining single major coins to try and earn a consistent profit. In both circumstances you won't even come close to earning back what you paid for the rig, and even if you could it's still more profitable to just buy the coins directly.
The rig prices would have to be much lower for a renter to make a profit. Either that or they have to e incredibly lucky. Even a basic statistical analysis based on profitability on CoinWarz shows that any renter at those prices is guaranteed to lose money.