Regardless of whether a new client has been referred by someone else that you already know and trust (implying that they are also going to behave like a 'good' client), I think you still need to adhere to a standard policy where a retainer of some sort is mandatory before you even commence the work.
I'm sorry this has happened to you, but it doesn't need to happen in the future. If someone is unwilling to provide a refundable retainer (according to your satisfaction guarantee) then I'm not sure you would want them as a client in the future.
It's okay to be upfront and unwaivering about your policies. I also believe that your clients will respect you more for it.
Karen
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