CEX.io is the best right now. You'll pay a bit of a premium, but no term, easy resale, and instant mining.
The website seems complex.Can I buy Ghash at any rate I set?I can even set 0.001 BTC per Ghash.Is that real?
It is very simple.
1) open account
2) fund the account with btc using the address they give you
3) when the funds are confirmed (about an hour) buy ghashes with your funds. The site shows buy orders and sell orders. You can buy at the current price, or enter an order to be executed at your price (if it comes down)
4) As soon as your buy order is executed, you own ghashes and they are instantly put to work mining. You will see your btc balance increase as they mine.
5) You can by almost any amount, down to fractions of ghashes.
Good luck!