It would be hard to make a profit by renting a rig and using a auto-exchanging pool. You would be better off renting a rig to speculate a newly released coin and dumping it when it hits some exchanges.
Take a look at poolpicker.eu for comparisons on auto-exchanging pools.
Take a look at poolpicker.eu for comparisons on auto-exchanging pools.
Mining and dumping isn't the only way to make money. Values of coins fluctuate significantly, and simply holding onto your coins for a couple weeks and picking your time to exchange can often net you much better results. That said, all multipools (and of course the alt coin market in general) are declining in profitability.
OP: I would be careful of Hashcows. I've had an unexchanged coin balance on their pool for like 3 weeks now. I've contacted them twice about it with no response. I'm tired of checking it every day waiting for them to exchange it. As it is, they have simply taxed me .017BTC; not much, but it's coin I earned.