The maintenance fee is deducted from your daily mining output each day and is 0.00028 USD per Gh/s for SHA 256 hashpower.
These are the current fees for these contracts and was updated January 24 2017.
Our terms can be viewed by doing the following.
1. Sign up to an account if you have not done so already.
2. Go to the screen to purchase hashpower, choose any amount over 50 USD, click continue.
3. The next screen should ask you to enter a promo code etc and also at the bottom will be a text box you can click on titled View Agreement.
You can then view the agreement. As you can also see, you did not have to actually purchase anything.