I am willing to put down 30% collateral for the bitcoin's current value.
The contract will guarantee the repayment of the same amount of bitcoins on completion, so you get back whatever you borrowed. If bitcoin goes up, you made that increase anyway.
Interest payments will be made monthly until expiry of contract in money/bitcoins.
I can demonstrate my ability to repay and willing to sign a contract to that effect.

Comparing to other loans: I can buy a house for just 5-20% deposit.