That Austin designer gave you good advice, but 25% might still be low. My kill fee is 50% for any project canceled after I start the work, no matter how far out it was booked. A 10% fee just covers a tiny bit of admin time, not the real lost income from turning other clients away. You have to make the client feel the cost of backing out, or they don't take the commitment seriously. It protects your schedule so you aren't left with a big empty spot you could have filled.

My own plant app just told me my cactus is depressed, so maybe don't ask me, @tessaw96.