Ok, then the best way to use your service is to get a free miner, wait until it generates enough btc to buy a minimal payed miner, buy it, and continue to withdraw profit once in a while without paying you a single satoshi from pocket. I am going to try this right now.
Or you could do some math and not waste your time. To buy 20 GH/s with proceeds from 10 GH/s will take a while. And if double ROI like that would be such an easy thing to do it would make even more sense to buy as many terrabytes as you can afford.