I used to make bridal gowns and formal wear. I got burned once, so I had my lawyer draw up the contract (he was a friend, so dinner was payment). I he told me I should charge a one time, non-refundable deposit. This covers the interview as to what the customer wanted. If they decided to go ahead with the project, that money was applied to the total balance. I had a lady come to me with a dress to be made. I plotted out every detail I could possibly think of. She ended up going to someone else, using my "design package". I was out almost 4 hours of time, putting samples together, patterns, notion prices. She used it as leverage to have the other seamstress do it for less.
I raised my prices and used the consultation fee. I told them about the fee before we would meet. Anyone not wanting to pay did not even get the consultation. I got a better class of client, and less bargin hunting hagglers.
I actually saw money coming in!