Because we had many upfront payment bad incidents, we had only one condition - payment ONLY after the result of 100% of the cost.
This is a bad idea for the person that will take the job. Sorry for your bad experience but you should secure the payment for the taker. The solution for this is to secure the payment through an escrow service.
The sequence would be, you send the fund to the escrow, you will wait for the job done until 100%, you will signal the escrow that you are satisfied and it's okay now to send the payment to the hired person. The escrow will send the payment to the taker, this is much more secure than your condition.